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* [PATCH] revert: optionally refer to commit in the "reference" format
@ 2022-05-22  4:32 Junio C Hamano
  2022-05-23 13:25 ` Johannes Schindelin
                   ` (3 more replies)
  0 siblings, 4 replies; 20+ messages in thread
From: Junio C Hamano @ 2022-05-22  4:32 UTC (permalink / raw)
  To: git

A typical "git revert" commit uses the full title of the original
commit in its title, and starts its body of the message with:

    This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.

This does not encourage the best practice of describing not just
"what" (i.e. "Revert X" on the title says what we did) but "why"
(i.e. and it does not say why X was undesirable).

We can instead phrase this first line of the body to be more like

    This reverts commit 8fa7f667 (do this and that, 2022-04-25)

so that the title does not have to be

    Revert "do this and that"

We can instead use the title to describe "why" we are reverting the
original commit.

Introduce the "--reference" option to "git revert", and also the
revert.reference configuration variable, which defaults to false, to
tweak the title and the first line of the draft commit message for
when creating a "revert" commit.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/config/revert.txt |  3 +++
 Documentation/git-revert.txt    |  9 +++++++++
 builtin/revert.c                |  2 ++
 sequencer.c                     | 32 +++++++++++++++++++++++++++-----
 sequencer.h                     |  1 +
 t/t3501-revert-cherry-pick.sh   | 31 +++++++++++++++++++++++++++++++
 6 files changed, 73 insertions(+), 5 deletions(-)
 create mode 100644 Documentation/config/revert.txt

diff --git a/Documentation/config/revert.txt b/Documentation/config/revert.txt
new file mode 100644
index 0000000000..797bfb6d62
--- /dev/null
+++ b/Documentation/config/revert.txt
@@ -0,0 +1,3 @@
+revert.reference::
+	Setting this variable to true makes `git revert` to behave
+	as if the `--reference` option is given.
diff --git a/Documentation/git-revert.txt b/Documentation/git-revert.txt
index bb92a4a451..8463fe9cf7 100644
--- a/Documentation/git-revert.txt
+++ b/Documentation/git-revert.txt
@@ -117,6 +117,15 @@ effect to your index in a row.
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--reference::
+	Instead of starting the body of the log message with "This
+	reverts <full object name of the commit being reverted>.",
+	refer to the commit using "--pretty=reference" format
+	(cf. linkgit:git-log[1]).  The `revert.reference`
+	configuration variable can be used to enable this option by
+	default.
+
+
 SEQUENCER SUBCOMMANDS
 ---------------------
 include::sequencer.txt[]
diff --git a/builtin/revert.c b/builtin/revert.c
index 51776abea6..ada51e46b9 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -116,6 +116,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 			N_("option for merge strategy"), option_parse_x),
 		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
 		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		OPT_BOOL(0, "reference", &opts->commit_use_reference,
+			 N_("use the 'reference' format to refer to commits")),
 		OPT_END()
 	};
 	struct option *options = base_options;
diff --git a/sequencer.c b/sequencer.c
index a5f678f452..97abd5932b 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -221,6 +221,9 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
 		return ret;
 	}
 
+	if (!strcmp(k, "revert.reference"))
+		opts->commit_use_reference = git_config_bool(k, v);
+
 	status = git_gpg_config(k, v, NULL);
 	if (status)
 		return status;
@@ -2059,6 +2062,20 @@ static int should_edit(struct replay_opts *opts) {
 	return opts->edit;
 }
 
+static void refer_to_commit(struct replay_opts *opts,
+			    struct strbuf *msgbuf, struct commit *commit)
+{
+	if (opts->commit_use_reference) {
+		struct pretty_print_context ctx = {
+			.abbrev = DEFAULT_ABBREV,
+			.date_mode.type = DATE_SHORT,
+		};
+		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);
+	} else {
+		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
+	}
+}
+
 static int do_pick_commit(struct repository *r,
 			  struct todo_item *item,
 			  struct replay_opts *opts,
@@ -2167,14 +2184,19 @@ static int do_pick_commit(struct repository *r,
 		base_label = msg.label;
 		next = parent;
 		next_label = msg.parent_label;
-		strbuf_addstr(&msgbuf, "Revert \"");
-		strbuf_addstr(&msgbuf, msg.subject);
-		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
-		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
+		if (!opts->commit_use_reference) {
+			strbuf_addstr(&msgbuf, "Revert \"");
+			strbuf_addstr(&msgbuf, msg.subject);
+			strbuf_addstr(&msgbuf, "\"");
+		} else {
+			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
+		}
+		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
+		refer_to_commit(opts, &msgbuf, commit);
 
 		if (commit->parents && commit->parents->next) {
 			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
-			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
+			refer_to_commit(opts, &msgbuf, parent);
 		}
 		strbuf_addstr(&msgbuf, ".\n");
 	} else {
diff --git a/sequencer.h b/sequencer.h
index da64473636..698599fe4e 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -49,6 +49,7 @@ struct replay_opts {
 	int reschedule_failed_exec;
 	int committer_date_is_author_date;
 	int ignore_date;
+	int commit_use_reference;
 
 	int mainline;
 
diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
index 8617efaaf1..36f9565b92 100755
--- a/t/t3501-revert-cherry-pick.sh
+++ b/t/t3501-revert-cherry-pick.sh
@@ -159,6 +159,7 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
 '
 
 test_expect_success 'advice from failed revert' '
+	test_when_finished "git reset --hard" &&
 	test_commit --no-tag "add dream" dream dream &&
 	dream_oid=$(git rev-parse --short HEAD) &&
 	cat <<-EOF >expected &&
@@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
 	test_must_fail git revert HEAD^ 2>actual &&
 	test_cmp expected actual
 '
+
+test_expect_success 'identification of reverted commit (vanilla)' '
+	test_commit to-ident &&
+	test_when_finished "git reset --hard to-ident" &&
+	git checkout --detach to-ident &&
+	git revert --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'identification of reverted commit (reference)' '
+	git checkout --detach to-ident &&
+	git revert --reference --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'identification of reverted commit (reference)' '
+	git checkout --detach to-ident &&
+	git -c revert.reference=true revert --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.36.1-298-g81715a4e6d


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-22  4:32 [PATCH] revert: optionally refer to commit in the "reference" format Junio C Hamano
@ 2022-05-23 13:25 ` Johannes Schindelin
  2022-05-23 22:48   ` Junio C Hamano
  2022-05-23 13:45 ` Ævar Arnfjörð Bjarmason
                   ` (2 subsequent siblings)
  3 siblings, 1 reply; 20+ messages in thread
From: Johannes Schindelin @ 2022-05-23 13:25 UTC (permalink / raw)
  To: Junio C Hamano; +Cc: git

Hi Junio,

On Sat, 21 May 2022, Junio C Hamano wrote:

> A typical "git revert" commit uses the full title of the original
> commit in its title, and starts its body of the message with:
>
>     This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.
>
> This does not encourage the best practice of describing not just
> "what" (i.e. "Revert X" on the title says what we did) but "why"
> (i.e. and it does not say why X was undesirable).
>
> We can instead phrase this first line of the body to be more like
>
>     This reverts commit 8fa7f667 (do this and that, 2022-04-25)
>
> so that the title does not have to be
>
>     Revert "do this and that"
>
> We can instead use the title to describe "why" we are reverting the
> original commit.

Good idea, the `reference` text is so much more pleasant to read (and it
also makes things somewhat proof against rebasing and transitioning to
SHA-256).

> Introduce the "--reference" option to "git revert", and also the
> revert.reference configuration variable, which defaults to false, to
> tweak the title and the first line of the draft commit message for
> when creating a "revert" commit.

At some stage, we may even default to `revert.reference=true`?

> diff --git a/Documentation/git-revert.txt b/Documentation/git-revert.txt
> index bb92a4a451..8463fe9cf7 100644
> --- a/Documentation/git-revert.txt
> +++ b/Documentation/git-revert.txt
> @@ -117,6 +117,15 @@ effect to your index in a row.
>  	Allow the rerere mechanism to update the index with the
>  	result of auto-conflict resolution if possible.
>
> +--reference::
> +	Instead of starting the body of the log message with "This
> +	reverts <full object name of the commit being reverted>.",
> +	refer to the commit using "--pretty=reference" format
> +	(cf. linkgit:git-log[1]).  The `revert.reference`
> +	configuration variable can be used to enable this option by
> +	default.
> +
> +

Is that extra empty line intentional?

>  SEQUENCER SUBCOMMANDS
>  ---------------------
>  include::sequencer.txt[]
> diff --git a/builtin/revert.c b/builtin/revert.c
> index 51776abea6..ada51e46b9 100644
> --- a/builtin/revert.c
> +++ b/builtin/revert.c
> @@ -116,6 +116,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
>  			N_("option for merge strategy"), option_parse_x),
>  		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
>  		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
> +		OPT_BOOL(0, "reference", &opts->commit_use_reference,
> +			 N_("use the 'reference' format to refer to commits")),
>  		OPT_END()
>  	};
>  	struct option *options = base_options;
> diff --git a/sequencer.c b/sequencer.c
> index a5f678f452..97abd5932b 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -221,6 +221,9 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
>  		return ret;
>  	}
>
> +	if (!strcmp(k, "revert.reference"))
> +		opts->commit_use_reference = git_config_bool(k, v);
> +
>  	status = git_gpg_config(k, v, NULL);
>  	if (status)
>  		return status;
> @@ -2059,6 +2062,20 @@ static int should_edit(struct replay_opts *opts) {
>  	return opts->edit;
>  }
>
> +static void refer_to_commit(struct replay_opts *opts,
> +			    struct strbuf *msgbuf, struct commit *commit)
> +{
> +	if (opts->commit_use_reference) {
> +		struct pretty_print_context ctx = {
> +			.abbrev = DEFAULT_ABBREV,
> +			.date_mode.type = DATE_SHORT,
> +		};
> +		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);

It is somewhat sad that we have to semi-duplicate [*1*] this format here
and do not have something like an enum value we can use instead.

> +	} else {
> +		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
> +	}
> +}
> +
>  static int do_pick_commit(struct repository *r,
>  			  struct todo_item *item,
>  			  struct replay_opts *opts,
> @@ -2167,14 +2184,19 @@ static int do_pick_commit(struct repository *r,
>  		base_label = msg.label;
>  		next = parent;
>  		next_label = msg.parent_label;
> -		strbuf_addstr(&msgbuf, "Revert \"");
> -		strbuf_addstr(&msgbuf, msg.subject);
> -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
> -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> +		if (!opts->commit_use_reference) {
> +			strbuf_addstr(&msgbuf, "Revert \"");
> +			strbuf_addstr(&msgbuf, msg.subject);
> +			strbuf_addstr(&msgbuf, "\"");
> +		} else {
> +			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
> +		}

We often tell newcomers that we prefer the shorter conditional block to
come first. Maybe you want to do that here, too? I don't mind the current
form, though.

> +		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
> +		refer_to_commit(opts, &msgbuf, commit);
>
>  		if (commit->parents && commit->parents->next) {
>  			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
> -			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
> +			refer_to_commit(opts, &msgbuf, parent);
>  		}
>  		strbuf_addstr(&msgbuf, ".\n");
>  	} else {
> diff --git a/sequencer.h b/sequencer.h
> index da64473636..698599fe4e 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -49,6 +49,7 @@ struct replay_opts {
>  	int reschedule_failed_exec;
>  	int committer_date_is_author_date;
>  	int ignore_date;
> +	int commit_use_reference;
>
>  	int mainline;
>
> diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
> index 8617efaaf1..36f9565b92 100755
> --- a/t/t3501-revert-cherry-pick.sh
> +++ b/t/t3501-revert-cherry-pick.sh
> @@ -159,6 +159,7 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
>  '
>
>  test_expect_success 'advice from failed revert' '
> +	test_when_finished "git reset --hard" &&
>  	test_commit --no-tag "add dream" dream dream &&
>  	dream_oid=$(git rev-parse --short HEAD) &&
>  	cat <<-EOF >expected &&
> @@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
>  	test_must_fail git revert HEAD^ 2>actual &&
>  	test_cmp expected actual
>  '
> +
> +test_expect_success 'identification of reverted commit (vanilla)' '

It might make sense to replace "vanilla" by "default format".

> +	test_commit to-ident &&
> +	test_when_finished "git reset --hard to-ident" &&
> +	git checkout --detach to-ident &&
> +	git revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&

I was a bit puzzled about this dance, as I had expected this instead:

	grep "^This reverts commit $(git rev-parse HEAD^)\\.$" actual.raw

but I guess you wanted to make sure that the file contents of `actual` are
shown if no match was found?

If that was the intention, we may want to add a test helper that I know
from other test frameworks, something like `test_contains` that takes a
regex and a file and prints out the full contents if no match was found.

It's obviously not necessary to add this test helper in this patch series
of a single patch ("separation of concerns"), just food for thought.

> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (reference)' '
> +	git checkout --detach to-ident &&
> +	git revert --reference --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'

If it was up to me, I would combine these three test cases, if only to
help the `--run=<single-number>` case (the latter two depend on the side
effect of the first one to create a `to-ident` tag).

> +
> +test_expect_success 'identification of reverted commit (reference)' '
> +	git checkout --detach to-ident &&
> +	git -c revert.reference=true revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
>  test_done
> --
> 2.36.1-298-g81715a4e6d

Looks good, I have no objections against merging this as-is.

Ciao,
Dscho

Footnote *1*: https://github.com/git/git/blob/v2.36.1/pretty.c#L103-L104
also has the `%C(auto)` prefix, which we obviously do not need here.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-22  4:32 [PATCH] revert: optionally refer to commit in the "reference" format Junio C Hamano
  2022-05-23 13:25 ` Johannes Schindelin
@ 2022-05-23 13:45 ` Ævar Arnfjörð Bjarmason
  2022-05-23 22:37   ` Junio C Hamano
  2022-05-26 11:17 ` Phillip Wood
  2022-06-26  9:29 ` René Scharfe
  3 siblings, 1 reply; 20+ messages in thread
From: Ævar Arnfjörð Bjarmason @ 2022-05-23 13:45 UTC (permalink / raw)
  To: Junio C Hamano; +Cc: git


On Sat, May 21 2022, Junio C Hamano wrote:

> A typical "git revert" commit uses the full title of the original
> commit in its title, and starts its body of the message with:
>
>     This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.
>
> This does not encourage the best practice of describing not just
> "what" (i.e. "Revert X" on the title says what we did) but "why"
> (i.e. and it does not say why X was undesirable).
>
> We can instead phrase this first line of the body to be more like
>
>     This reverts commit 8fa7f667 (do this and that, 2022-04-25)
>
> so that the title does not have to be
>
>     Revert "do this and that"
>
> We can instead use the title to describe "why" we are reverting the
> original commit.
>
> Introduce the "--reference" option to "git revert", and also the
> revert.reference configuration variable, which defaults to false, to
> tweak the title and the first line of the draft commit message for
> when creating a "revert" commit.

This is fantastic, I've wanted to fix this particular nit for a long
time.

> +static void refer_to_commit(struct replay_opts *opts,
> +			    struct strbuf *msgbuf, struct commit *commit)
> +{
> +	if (opts->commit_use_reference) {
> +		struct pretty_print_context ctx = {
> +			.abbrev = DEFAULT_ABBREV,
> +			.date_mode.type = DATE_SHORT,
> +		};
> +		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);
> +	} else {
> +		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
> +	}
> +}
> +
>  static int do_pick_commit(struct repository *r,
>  			  struct todo_item *item,
>  			  struct replay_opts *opts,
> @@ -2167,14 +2184,19 @@ static int do_pick_commit(struct repository *r,
>  		base_label = msg.label;
>  		next = parent;
>  		next_label = msg.parent_label;
> -		strbuf_addstr(&msgbuf, "Revert \"");
> -		strbuf_addstr(&msgbuf, msg.subject);
> -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
> -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> +		if (!opts->commit_use_reference) {
> +			strbuf_addstr(&msgbuf, "Revert \"");
> +			strbuf_addstr(&msgbuf, msg.subject);
> +			strbuf_addstr(&msgbuf, "\"");
> +		} else {
> +			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");

Having seen how people use git in the wild, this *WILL* result in a
bunch of history where people don't edit that at all.

If we want them to edit something we should come up with a buffer that's
empty except for suggested #-commented parts, and suggest that they
uncomment/edit some of it.

I also use "git revert --no-edit" in my own workflow, e.g. when
reverting back and forth in WIP code, having the OID is useful, having
this new "reference" would be even better, but having that just in the
body and "DESCRIBE WHY..." in the %s would be much less useful.

> +		}
> +		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
> +		refer_to_commit(opts, &msgbuf, commit);
>  
>  		if (commit->parents && commit->parents->next) {
>  			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
> -			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
> +			refer_to_commit(opts, &msgbuf, parent);
>  		}
>  		strbuf_addstr(&msgbuf, ".\n");
>  	} else {

This is very POC, but I wish we had something like the WIP diff at the
end of this E-Mail (which is a mess, I was experimenting). I.e. we'd
always emit (when this setting is enabled)

    Revert %h (%s, %ad)

Except that the %s and the rest of the line would use the truncation
feature of "git log" formats, and would make sure the line isn't longer
than so-and-so, e.g. 72 or 50 characters.

Then only if we truncated things there, or we have parents to mention
would we add a body like:

    This reverts commit %h (%s, %ad)

Followed by "reversing changes..."

All of which would be much easier than the below monstrosity I came up
with if:

 1. You could ask "git log" formats to not whitespace pad the
    truncation, I couldn't find a way to do that (but it's the first
    time I use it).

 2. We just had some generic "wrap this buffer" function, maybe we do, I
    didn't look much.

> diff --git a/sequencer.h b/sequencer.h
> index da64473636..698599fe4e 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -49,6 +49,7 @@ struct replay_opts {
>  	int reschedule_failed_exec;
>  	int committer_date_is_author_date;
>  	int ignore_date;
> +	int commit_use_reference;
>  
>  	int mainline;
>  
> diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
> index 8617efaaf1..36f9565b92 100755
> --- a/t/t3501-revert-cherry-pick.sh
> +++ b/t/t3501-revert-cherry-pick.sh
> @@ -159,6 +159,7 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
>  '
>  
>  test_expect_success 'advice from failed revert' '
> +	test_when_finished "git reset --hard" &&
>  	test_commit --no-tag "add dream" dream dream &&
>  	dream_oid=$(git rev-parse --short HEAD) &&
>  	cat <<-EOF >expected &&
> @@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
>  	test_must_fail git revert HEAD^ 2>actual &&
>  	test_cmp expected actual
>  '
> +
> +test_expect_success 'identification of reverted commit (vanilla)' '
> +	test_commit to-ident &&
> +	test_when_finished "git reset --hard to-ident" &&
> +	git checkout --detach to-ident &&
> +	git revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (reference)' '
> +	git checkout --detach to-ident &&
> +	git revert --reference --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&

This hides the exit code of the embedded $() git command.

Re the suggested changes below: let's just test_cmp the whole thing,
subject+body instead?

> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (reference)' '
> +	git checkout --detach to-ident &&
> +	git -c revert.reference=true revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
>  test_done


diff --git a/sequencer.c b/sequencer.c
index 4abb77add09..a43444e2339 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2061,18 +2061,14 @@ static int should_edit(struct replay_opts *opts) {
 	return opts->edit;
 }
 
-static void refer_to_commit(struct replay_opts *opts,
-			    struct strbuf *msgbuf, struct commit *commit)
-{
-	if (opts->commit_use_reference) {
-		struct pretty_print_context ctx = {
-			.abbrev = DEFAULT_ABBREV,
-			.date_mode.type = DATE_SHORT,
-		};
-		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);
-	} else {
-		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
-	}
+static void refer_to_commit(struct strbuf *sb, struct commit *commit,
+			    const char *const fmt)
+{
+	struct pretty_print_context ctx = {
+		.abbrev = DEFAULT_ABBREV,
+		.date_mode.type = DATE_SHORT,
+	};
+	format_commit_message(commit, fmt, sb, &ctx);
 }
 
 static int do_pick_commit(struct repository *r,
@@ -2183,19 +2179,63 @@ static int do_pick_commit(struct repository *r,
 		base_label = msg.label;
 		next = parent;
 		next_label = msg.parent_label;
-		if (!opts->commit_use_reference) {
+		if (opts->commit_use_reference) {
+			struct strbuf sb_b = STRBUF_INIT;
+			struct strbuf sb_h = STRBUF_INIT;
+			struct strbuf sb_ad = STRBUF_INIT;
+			struct strbuf sb_s = STRBUF_INIT;
+			struct strbuf sb_s_t = STRBUF_INIT;
+			const size_t wraplen = 72;
+			char *fmt;
+			size_t len = wraplen;
+			int truncated;
+
+			refer_to_commit(&sb_h, commit, "Revert %h (");
+			len -= sb_h.len;
+			refer_to_commit(&sb_ad, commit, "%ad)");
+			len -= sb_ad.len;
+			len -= 2 ; /* The ", " in: Revert %h (%s, %ad) */
+			/* vanilla %h (%s, %ad) */
+			refer_to_commit(&sb_s, commit, "%s");
+
+			/* truncated %h (%s, %ad) */
+			fmt = xstrfmt("%%<(%d,trunc)%%s", (int)len);
+			refer_to_commit(&sb_s_t, commit, fmt);
+			free(fmt);
+			strbuf_rtrim(&sb_s_t);
+
+			truncated = strcmp(sb_s.buf, sb_s_t.buf);
+
+			strbuf_addbuf(&msgbuf, &sb_h);
+			strbuf_addbuf(&msgbuf, &sb_s_t);
+			strbuf_addbuf(&msgbuf, &sb_ad);
+			strbuf_addstr(&msgbuf, "\n\n");
+
+			if (truncated) {
+				const char *pfx = "This reverts commit ";
+				size_t len = wraplen - strlen(pfx); /* TODO: Consider %h etc. */
+				char *fmt;
+				
+				fmt = xstrfmt("%s%%h (%%w(%d,0,0)%%s, %%ad)",
+					      pfx, (int)len);
+				refer_to_commit(&sb_b, commit, fmt);
+				free(fmt);
+				strbuf_addbuf(&msgbuf, &sb_b);
+			} else {
+				/* TODO: The not-truncated version ... */
+			}
+		} else {
 			strbuf_addstr(&msgbuf, "Revert \"");
 			strbuf_addstr(&msgbuf, msg.subject);
 			strbuf_addstr(&msgbuf, "\"");
-		} else {
-			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
-		}
-		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
-		refer_to_commit(opts, &msgbuf, commit);
+			strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
+			strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
 
-		if (commit->parents && commit->parents->next) {
-			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
-			refer_to_commit(opts, &msgbuf, parent);
+			if (commit->parents && commit->parents->next) {
+				/* TODO: Handle the wrapping of this too... */
+				strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
+				strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
+			}
 		}
 		strbuf_addstr(&msgbuf, ".\n");
 	} else {

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-23 13:45 ` Ævar Arnfjörð Bjarmason
@ 2022-05-23 22:37   ` Junio C Hamano
  2022-05-24  8:12     ` Ævar Arnfjörð Bjarmason
  0 siblings, 1 reply; 20+ messages in thread
From: Junio C Hamano @ 2022-05-23 22:37 UTC (permalink / raw)
  To: Ævar Arnfjörð Bjarmason; +Cc: git

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

>> +		if (!opts->commit_use_reference) {
>> +			strbuf_addstr(&msgbuf, "Revert \"");
>> +			strbuf_addstr(&msgbuf, msg.subject);
>> +			strbuf_addstr(&msgbuf, "\"");
>> +		} else {
>> +			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
>
> Having seen how people use git in the wild, this *WILL* result in a
> bunch of history where people don't edit that at all.

It was done very much on purpose.  A pressure from other project
participants against the ugly all caps content-free message will
help instill better behaviour.  A solo developer also will learn
after making reverts with content-free titles (and if they do not
find it inconvenient for their development purpose that their
history is full of content-free titles shouting in all caps, then
more power to them---if they are happy, we are happy, too).

If we leave something like

	# Add one line above and explain not *what* this revert did,
	# but *why* you decided to revert in 50-70 chars.  Did it
	# break something? Was it premature?

	This reverts commit 8aa3f0dc (CI: set CC in MAKEFLAGS directly, 2022-04-21)

presumably, stripspace will make the "This reverts commit ..." the
title of the reverted commit.  It would invite people not to edit it
out out of laziness.  Since the whole point of this change is to
encourage people to describe the reason behind the revert on the
subject line, such an invitation is counter-productive.

Doing the first two lines like so:

	Revert 8aa3f0dc (CI: set CC in MAKEFLAGS directly, 2022-04-21)
	# Edit the above line to explain not *what* this revert did,

would have pretty much the same effect, I am afraid.

So...

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-23 13:25 ` Johannes Schindelin
@ 2022-05-23 22:48   ` Junio C Hamano
  2022-05-27  6:01     ` [PATCH v3] " Junio C Hamano
  2022-05-30 16:50     ` Side effects in Git's test suite, was Re: [PATCH] " Johannes Schindelin
  0 siblings, 2 replies; 20+ messages in thread
From: Junio C Hamano @ 2022-05-23 22:48 UTC (permalink / raw)
  To: Johannes Schindelin; +Cc: git

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Good idea, the `reference` text is so much more pleasant to read (and it
> also makes things somewhat proof against rebasing and transitioning to
> SHA-256).

Never thought of that myself.  It does sound like another good
reason to see if this is a good alternative format to use.

> At some stage, we may even default to `revert.reference=true`?

Perhaps.  Wasn't planning to propose that in any near future,
either, though.  I would prefer to never think about changing the
default in the future when considering a new feature.  It should be
done as two separate steps (except that care must be taken so that
the feature could become default if we choose to).

>> +--reference::
>> ...
>> +	default.
>> +
>> +
>
> Is that extra empty line intentional?

It is very much so.  A single blank between each items in the
section, a larger blank between two sections, is what I aimed at
here.

>> +		if (!opts->commit_use_reference) {
>> +			strbuf_addstr(&msgbuf, "Revert \"");
>> +			strbuf_addstr(&msgbuf, msg.subject);
>> +			strbuf_addstr(&msgbuf, "\"");
>> +		} else {
>> +			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
>> +		}
>
> We often tell newcomers that we prefer the shorter conditional block to
> come first. Maybe you want to do that here, too? I don't mind the current
> form, though.

Good point, but that is more applicable to new code (and not limited
to newcomers).  We also tell that your new feature is often not any
more important than the existing code, and think twice before
prepending the new code to existing code (iow, by default new code
should be appended, unless there is a good reason not to).

I kept the original behaviour first with optional new action as a
follow-up.  Besides, 3-line block is not all that larger than a
single-line block, and this did not trigger my "that one is larger"
sensor.

Let me try swapping the order.

>> @@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
>>  	test_must_fail git revert HEAD^ 2>actual &&
>>  	test_cmp expected actual
>>  '
>> +
>> +test_expect_success 'identification of reverted commit (vanilla)' '
>
> It might make sense to replace "vanilla" by "default format".

Sounds very sensible; thanks.

>> +	test_commit to-ident &&
>> +	test_when_finished "git reset --hard to-ident" &&
>> +	git checkout --detach to-ident &&
>> +	git revert --no-edit HEAD &&
>> +	git cat-file commit HEAD >actual.raw &&
>> +	grep "^This reverts " actual.raw >actual &&
>> +	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&
>
> I was a bit puzzled about this dance, as I had expected this instead:
>
> 	grep "^This reverts commit $(git rev-parse HEAD^)\\.$" actual.raw
>
> but I guess you wanted to make sure that the file contents of `actual` are
> shown if no match was found?

My thought process was much simpler.

"^This reverts" is common in both formats, so grep would extract the
commit reference(s) the command would have made to "actual".

What we need to make sure with the test_cmp are multifold.  We want
to make sure that the reference is made in the right format, refers
to the right commit, and we show the reference exactly the expected
number (i.e. one) of times.  So it was simpler to do so in a step
separate from the "extraction" step above.  We could go looser and
use test_contains but I usually try to avoid deliberately to be
loose.

>> +test_expect_success 'identification of reverted commit (reference)' '
>> +	git checkout --detach to-ident &&
>> +	git revert --reference --no-edit HEAD &&
>> +	git cat-file commit HEAD >actual.raw &&
>> +	grep "^This reverts " actual.raw >actual &&
>> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
>> +	test_cmp expect actual
>> +'
>
> If it was up to me, I would combine these three test cases, if only to
> help the `--run=<single-number>` case (the latter two depend on the side
> effect of the first one to create a `to-ident` tag).

I wonder if our prereq infrastructure is lightweight and scalable
enough so that we can easily add a support a pseudo-prerequisite
PREVIOUS that lets us say

	test_expect_success PREVIOUS "identification ..." '
		...
	'

to mean that this test requires the previous test has not been
skipped.

Then we can organize them into four (one to create to-ident commit,
one uses vanilla, one uses --reference and one uses revert.reference),
and make the latter three depend on their previous step.

>> +test_expect_success 'identification of reverted commit (reference)' '
>> +	git checkout --detach to-ident &&
>> +	git -c revert.reference=true revert --no-edit HEAD &&
>> +	git cat-file commit HEAD >actual.raw &&
>> +	grep "^This reverts " actual.raw >actual &&
>> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
>> +	test_cmp expect actual
>> +'
>> +
>>  test_done

Thanks for taking a look.

--- >8 ---
Subject: [PATCH v2] revert: optionally refer to commit in the "reference" format

A typical "git revert" commit uses the full title of the original
commit in its title, and starts its body of the message with:

    This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.

This does not encourage the best practice of describing not just
"what" (i.e. "Revert X" on the title says what we did) but "why"
(i.e. and it does not say why X was undesirable).

We can instead phrase this first line of the body to be more like

    This reverts commit 8fa7f667 (do this and that, 2022-04-25)

so that the title does not have to be

    Revert "do this and that"

We can instead use the title to describe "why" we are reverting the
original commit.

Introduce the "--reference" option to "git revert", and also the
revert.reference configuration variable, which defaults to false, to
tweak the title and the first line of the draft commit message for
when creating a "revert" commit.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
Range-diff:
1:  26b60b56c0 ! 1:  c5b11efe7d revert: optionally refer to commit in the "reference" format
    @@ sequencer.c: static int do_pick_commit(struct repository *r,
     -		strbuf_addstr(&msgbuf, msg.subject);
     -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
     -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
    -+		if (!opts->commit_use_reference) {
    ++		if (opts->commit_use_reference) {
    ++			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
    ++		} else {
     +			strbuf_addstr(&msgbuf, "Revert \"");
     +			strbuf_addstr(&msgbuf, msg.subject);
     +			strbuf_addstr(&msgbuf, "\"");
    -+		} else {
    -+			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
     +		}
     +		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
     +		refer_to_commit(opts, &msgbuf, commit);
    @@ t/t3501-revert-cherry-pick.sh: test_expect_success 'advice from failed revert' '
      	test_cmp expected actual
      '
     +
    -+test_expect_success 'identification of reverted commit (vanilla)' '
    ++test_expect_success 'identification of reverted commit (default)' '
     +	test_commit to-ident &&
     +	test_when_finished "git reset --hard to-ident" &&
     +	git checkout --detach to-ident &&
    @@ t/t3501-revert-cherry-pick.sh: test_expect_success 'advice from failed revert' '
     +	test_cmp expect actual
     +'
     +
    -+test_expect_success 'identification of reverted commit (reference)' '
    ++test_expect_success 'identification of reverted commit (--reference)' '
     +	git checkout --detach to-ident &&
     +	git revert --reference --no-edit HEAD &&
     +	git cat-file commit HEAD >actual.raw &&
    @@ t/t3501-revert-cherry-pick.sh: test_expect_success 'advice from failed revert' '
     +	test_cmp expect actual
     +'
     +
    -+test_expect_success 'identification of reverted commit (reference)' '
    ++test_expect_success 'identification of reverted commit (revert.reference)' '
     +	git checkout --detach to-ident &&
     +	git -c revert.reference=true revert --no-edit HEAD &&
     +	git cat-file commit HEAD >actual.raw &&

 Documentation/config/revert.txt |  3 +++
 Documentation/git-revert.txt    |  9 +++++++++
 builtin/revert.c                |  2 ++
 sequencer.c                     | 32 +++++++++++++++++++++++++++-----
 sequencer.h                     |  1 +
 t/t3501-revert-cherry-pick.sh   | 31 +++++++++++++++++++++++++++++++
 6 files changed, 73 insertions(+), 5 deletions(-)
 create mode 100644 Documentation/config/revert.txt

diff --git a/Documentation/config/revert.txt b/Documentation/config/revert.txt
new file mode 100644
index 0000000000..797bfb6d62
--- /dev/null
+++ b/Documentation/config/revert.txt
@@ -0,0 +1,3 @@
+revert.reference::
+	Setting this variable to true makes `git revert` to behave
+	as if the `--reference` option is given.
diff --git a/Documentation/git-revert.txt b/Documentation/git-revert.txt
index bb92a4a451..8463fe9cf7 100644
--- a/Documentation/git-revert.txt
+++ b/Documentation/git-revert.txt
@@ -117,6 +117,15 @@ effect to your index in a row.
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--reference::
+	Instead of starting the body of the log message with "This
+	reverts <full object name of the commit being reverted>.",
+	refer to the commit using "--pretty=reference" format
+	(cf. linkgit:git-log[1]).  The `revert.reference`
+	configuration variable can be used to enable this option by
+	default.
+
+
 SEQUENCER SUBCOMMANDS
 ---------------------
 include::sequencer.txt[]
diff --git a/builtin/revert.c b/builtin/revert.c
index 51776abea6..ada51e46b9 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -116,6 +116,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 			N_("option for merge strategy"), option_parse_x),
 		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
 		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		OPT_BOOL(0, "reference", &opts->commit_use_reference,
+			 N_("use the 'reference' format to refer to commits")),
 		OPT_END()
 	};
 	struct option *options = base_options;
diff --git a/sequencer.c b/sequencer.c
index a5f678f452..92d301f0c4 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -221,6 +221,9 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
 		return ret;
 	}
 
+	if (!strcmp(k, "revert.reference"))
+		opts->commit_use_reference = git_config_bool(k, v);
+
 	status = git_gpg_config(k, v, NULL);
 	if (status)
 		return status;
@@ -2059,6 +2062,20 @@ static int should_edit(struct replay_opts *opts) {
 	return opts->edit;
 }
 
+static void refer_to_commit(struct replay_opts *opts,
+			    struct strbuf *msgbuf, struct commit *commit)
+{
+	if (opts->commit_use_reference) {
+		struct pretty_print_context ctx = {
+			.abbrev = DEFAULT_ABBREV,
+			.date_mode.type = DATE_SHORT,
+		};
+		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);
+	} else {
+		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
+	}
+}
+
 static int do_pick_commit(struct repository *r,
 			  struct todo_item *item,
 			  struct replay_opts *opts,
@@ -2167,14 +2184,19 @@ static int do_pick_commit(struct repository *r,
 		base_label = msg.label;
 		next = parent;
 		next_label = msg.parent_label;
-		strbuf_addstr(&msgbuf, "Revert \"");
-		strbuf_addstr(&msgbuf, msg.subject);
-		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
-		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
+		if (opts->commit_use_reference) {
+			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
+		} else {
+			strbuf_addstr(&msgbuf, "Revert \"");
+			strbuf_addstr(&msgbuf, msg.subject);
+			strbuf_addstr(&msgbuf, "\"");
+		}
+		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
+		refer_to_commit(opts, &msgbuf, commit);
 
 		if (commit->parents && commit->parents->next) {
 			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
-			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
+			refer_to_commit(opts, &msgbuf, parent);
 		}
 		strbuf_addstr(&msgbuf, ".\n");
 	} else {
diff --git a/sequencer.h b/sequencer.h
index da64473636..698599fe4e 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -49,6 +49,7 @@ struct replay_opts {
 	int reschedule_failed_exec;
 	int committer_date_is_author_date;
 	int ignore_date;
+	int commit_use_reference;
 
 	int mainline;
 
diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
index 8617efaaf1..a386ae9e88 100755
--- a/t/t3501-revert-cherry-pick.sh
+++ b/t/t3501-revert-cherry-pick.sh
@@ -159,6 +159,7 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
 '
 
 test_expect_success 'advice from failed revert' '
+	test_when_finished "git reset --hard" &&
 	test_commit --no-tag "add dream" dream dream &&
 	dream_oid=$(git rev-parse --short HEAD) &&
 	cat <<-EOF >expected &&
@@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
 	test_must_fail git revert HEAD^ 2>actual &&
 	test_cmp expected actual
 '
+
+test_expect_success 'identification of reverted commit (default)' '
+	test_commit to-ident &&
+	test_when_finished "git reset --hard to-ident" &&
+	git checkout --detach to-ident &&
+	git revert --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'identification of reverted commit (--reference)' '
+	git checkout --detach to-ident &&
+	git revert --reference --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'identification of reverted commit (revert.reference)' '
+	git checkout --detach to-ident &&
+	git -c revert.reference=true revert --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.36.1-312-ge077cd1662


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-23 22:37   ` Junio C Hamano
@ 2022-05-24  8:12     ` Ævar Arnfjörð Bjarmason
  2022-05-24 19:11       ` Junio C Hamano
  0 siblings, 1 reply; 20+ messages in thread
From: Ævar Arnfjörð Bjarmason @ 2022-05-24  8:12 UTC (permalink / raw)
  To: Junio C Hamano; +Cc: git


On Mon, May 23 2022, Junio C Hamano wrote:

> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>
>>> +		if (!opts->commit_use_reference) {
>>> +			strbuf_addstr(&msgbuf, "Revert \"");
>>> +			strbuf_addstr(&msgbuf, msg.subject);
>>> +			strbuf_addstr(&msgbuf, "\"");
>>> +		} else {
>>> +			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
>>
>> Having seen how people use git in the wild, this *WILL* result in a
>> bunch of history where people don't edit that at all.
>
> It was done very much on purpose.  A pressure from other project
> participants against the ugly all caps content-free message will
> help instill better behaviour.

In some cases that will happen, but from experience of working with a
bunch of novice git users some people won't edit these at all,
particularly when they're in a rush (e.g. reverting something because a
thing broke production).

So making the default subject less useful is something that will be seen
by others, and thus result in worse UX.

AFAICT all of the goals you're suggesting here will be even better if
it's commented out, then you will need to edit it, and we'll error out
by default if you don't. Why not use that?

> A solo developer also will learn
> after making reverts with content-free titles (and if they do not
> find it inconvenient for their development purpose that their
> history is full of content-free titles shouting in all caps, then
> more power to them---if they are happy, we are happy, too).

The subject you're replacing isn't content-free, it at least includes
the OID, this one doesn't, so you won't see it in --oneline. That's less
useful.

> If we leave something like
>
> 	# Add one line above and explain not *what* this revert did,
> 	# but *why* you decided to revert in 50-70 chars.  Did it
> 	# break something? Was it premature?
>
> 	This reverts commit 8aa3f0dc (CI: set CC in MAKEFLAGS directly, 2022-04-21)
>
> presumably, stripspace will make the "This reverts commit ..." the
> title of the reverted commit.  It would invite people not to edit it
> out out of laziness.  Since the whole point of this change is to
> encourage people to describe the reason behind the revert on the
> subject line, such an invitation is counter-productive.

If that's the concern we could also comment the "This reverts" line.

> Doing the first two lines like so:
>
> 	Revert 8aa3f0dc (CI: set CC in MAKEFLAGS directly, 2022-04-21)
> 	# Edit the above line to explain not *what* this revert did,
>
> would have pretty much the same effect, I am afraid.
>
> So...

Ditto, so just present a buffer like:

    # Revert 8aa3f0dc (CI: set CC in MAKEFLAGS directly, 2022-04-21)
    #
    # This reverts commit 8aa3f0dc (CI: set CC in MAKEFLAGS directly, 2022-04-21)

Along with some advice that the user can uncomment those template lines
& adjust them.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-24  8:12     ` Ævar Arnfjörð Bjarmason
@ 2022-05-24 19:11       ` Junio C Hamano
  0 siblings, 0 replies; 20+ messages in thread
From: Junio C Hamano @ 2022-05-24 19:11 UTC (permalink / raw)
  To: Ævar Arnfjörð Bjarmason; +Cc: git

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

> AFAICT all of the goals you're suggesting here will be even better if
> it's commented out, then you will need to edit it, and we'll error out
> by default if you don't. Why not use that?

Simply because I doubt that would work.  Doesn't the stripspace on
the log message with unedited comments simply discard the commented
out part and results in a title that is taken from the line that
happens to end up being the first non-blank-non-commented-out line?

> The subject you're replacing isn't content-free, it at least includes
> the OID, this one doesn't, so you won't see it in --oneline. That's less
> useful.

I know.  That is the point; those who choose to use --reference want
to make sure they want to edit out the line that tell them to edit.

>
>> If we leave something like
>>
>> 	# Add one line above and explain not *what* this revert did,
>> 	# but *why* you decided to revert in 50-70 chars.  Did it
>> 	# break something? Was it premature?
>>
>> 	This reverts commit 8aa3f0dc (CI: set CC in MAKEFLAGS directly, 2022-04-21)
>>
>> presumably, stripspace will make the "This reverts commit ..." the
>> title of the reverted commit.  It would invite people not to edit it
>> out out of laziness.  Since the whole point of this change is to
>> encourage people to describe the reason behind the revert on the
>> subject line, such an invitation is counter-productive.
>
> If that's the concern we could also comment the "This reverts" line.

That punishes the normal use case where the title is edited and the
body is used to start the message as-is.


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-22  4:32 [PATCH] revert: optionally refer to commit in the "reference" format Junio C Hamano
  2022-05-23 13:25 ` Johannes Schindelin
  2022-05-23 13:45 ` Ævar Arnfjörð Bjarmason
@ 2022-05-26 11:17 ` Phillip Wood
  2022-05-26 17:29   ` Junio C Hamano
  2022-06-26  9:29 ` René Scharfe
  3 siblings, 1 reply; 20+ messages in thread
From: Phillip Wood @ 2022-05-26 11:17 UTC (permalink / raw)
  To: Junio C Hamano, git

Hi Junio

On 22/05/2022 05:32, Junio C Hamano wrote:
> A typical "git revert" commit uses the full title of the original
> commit in its title, and starts its body of the message with:
> 
>      This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.
> 
> This does not encourage the best practice of describing not just
> "what" (i.e. "Revert X" on the title says what we did) but "why"
> (i.e. and it does not say why X was undesirable).
> 
> We can instead phrase this first line of the body to be more like
> 
>      This reverts commit 8fa7f667 (do this and that, 2022-04-25)
> 
> so that the title does not have to be
> 
>      Revert "do this and that"
> 
> We can instead use the title to describe "why" we are reverting the
> original commit.
> 
> Introduce the "--reference" option to "git revert", and also the
> revert.reference configuration variable, which defaults to false, to
> tweak the title and the first line of the draft commit message for
> when creating a "revert" commit.

I think this is a good idea which will hopefully improve project histories.

> diff --git a/builtin/revert.c b/builtin/revert.c
> index 51776abea6..ada51e46b9 100644
> --- a/builtin/revert.c
> +++ b/builtin/revert.c
> @@ -116,6 +116,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
>   			N_("option for merge strategy"), option_parse_x),
>   		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
>   		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
> +		OPT_BOOL(0, "reference", &opts->commit_use_reference,
> +			 N_("use the 'reference' format to refer to commits")),

This option is being added to base_options which applies to cherry-pick 
as well as revert. There is a "if" statement just below this hunk which 
adds cherry-pick specific options, I think we want to add this new 
option in an else block added to that "if" statement.

>   static int do_pick_commit(struct repository *r,
>   			  struct todo_item *item,
>   			  struct replay_opts *opts,
> @@ -2167,14 +2184,19 @@ static int do_pick_commit(struct repository *r,
>   		base_label = msg.label;
>   		next = parent;
>   		next_label = msg.parent_label;
> -		strbuf_addstr(&msgbuf, "Revert \"");
> -		strbuf_addstr(&msgbuf, msg.subject);
> -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
> -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> +		if (!opts->commit_use_reference) {
> +			strbuf_addstr(&msgbuf, "Revert \"");
> +			strbuf_addstr(&msgbuf, msg.subject);
> +			strbuf_addstr(&msgbuf, "\"");
> +		} else {
> +			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");

In format-patch we add three asterisks to the beginning and end of the 
dummy subject and body lines to encourage the user to edit them - is 
that worth doing here as well?

Best Wishes

Phillip

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-26 11:17 ` Phillip Wood
@ 2022-05-26 17:29   ` Junio C Hamano
  0 siblings, 0 replies; 20+ messages in thread
From: Junio C Hamano @ 2022-05-26 17:29 UTC (permalink / raw)
  To: Phillip Wood; +Cc: git

Phillip Wood <phillip.wood123@gmail.com> writes:

> In format-patch we add three asterisks to the beginning and end of the
> dummy subject and body lines to encourage the user to edit them - is 
> that worth doing here as well?

Yeah, that would make things consistent.

I am still mulling over Ævar's idea of preparing the messsage in
such a way that, if committed without editing, the title becomes
identifiable but too ugly to force users consider rewording (and the
"identifiable" part helps the "rebase -i" process), while making it
easy to discard the instruction for the user who do want to edit.  I
think that is the right approach, if we can find one.  What has been
floated on the list during the discussion is not there yet, but I
think the approach is a good one.

Thanks.


^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH v3] revert: optionally refer to commit in the "reference" format
  2022-05-23 22:48   ` Junio C Hamano
@ 2022-05-27  6:01     ` Junio C Hamano
  2022-05-30 16:40       ` Johannes Schindelin
                         ` (2 more replies)
  2022-05-30 16:50     ` Side effects in Git's test suite, was Re: [PATCH] " Johannes Schindelin
  1 sibling, 3 replies; 20+ messages in thread
From: Junio C Hamano @ 2022-05-27  6:01 UTC (permalink / raw)
  To: git
  Cc: Johannes Schindelin, Phillip Wood,
	Ævar Arnfjörð Bjarmason

A typical "git revert" commit uses the full title of the original
commit in its title, and starts its body of the message with:

    This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.

This does not encourage the best practice of describing not just
"what" (i.e. "Revert X" on the title says what we did) but "why"
(i.e. and it does not say why X was undesirable).

We can instead phrase this first line of the body to be more like

    This reverts commit 8fa7f667 (do this and that, 2022-04-25)

so that the title does not have to be

    Revert "do this and that"

We can instead use the title to describe "why" we are reverting the
original commit.

Introduce the "--reference" option to "git revert", and also the
revert.reference configuration variable, which defaults to false, to
tweak the title and the first line of the draft commit message for
when creating a "revert" commit.

When this option is in use, the first line of the pre-filled editor
buffer becomes a comment line that tells the user to say _why_.  If
the user exits the editor without touching this line by mistake,
what we prepare to become the first line of the body, i.e. "This
reverts commit 8fa7f667 (do this and that, 2022-04-25)", ends up to
be the title of the resulting commit.  This behaviour is designed to
help such a user to identify such a revert in "git log --oneline"
easily so that it can be further reworded with "git rebase -i" later.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 * The only difference since the second one is that the first line of
   the log message template is commented out and has asterisks to
   draw more attention.  The last paragraph (new) in the proposed
   log message explains the rationale behind this design.

   Third-time a charm, hopefully.

Range-diff against v2:
1:  4152fc2092 ! 1:  f4325a503a revert: optionally refer to commit in the "reference" format
    @@ Commit message
         tweak the title and the first line of the draft commit message for
         when creating a "revert" commit.
     
    +    When this option is in use, the first line of the pre-filled editor
    +    buffer becomes a comment line that tells the user to say _why_.  If
    +    the user exits the editor without touching this line by mistake,
    +    what we prepare to become the first line of the body, i.e. "This
    +    reverts commit 8fa7f667 (do this and that, 2022-04-25)", ends up to
    +    be the title of the resulting commit.  This behaviour is designed to
    +    help such a user to identify such a revert in "git log --oneline"
    +    easily so that it can be further reworded with "git rebase -i" later.
    +
         Signed-off-by: Junio C Hamano <gitster@pobox.com>
     
      ## Documentation/config/revert.txt (new) ##
    @@ sequencer.c: static int do_pick_commit(struct repository *r,
     -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
     -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
     +		if (opts->commit_use_reference) {
    -+			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
    ++			strbuf_addstr(&msgbuf,
    ++				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
     +		} else {
     +			strbuf_addstr(&msgbuf, "Revert \"");
     +			strbuf_addstr(&msgbuf, msg.subject);

 Documentation/config/revert.txt |  3 +++
 Documentation/git-revert.txt    |  9 +++++++++
 builtin/revert.c                |  2 ++
 sequencer.c                     | 33 ++++++++++++++++++++++++++++-----
 sequencer.h                     |  1 +
 t/t3501-revert-cherry-pick.sh   | 31 +++++++++++++++++++++++++++++++
 6 files changed, 74 insertions(+), 5 deletions(-)
 create mode 100644 Documentation/config/revert.txt

diff --git a/Documentation/config/revert.txt b/Documentation/config/revert.txt
new file mode 100644
index 0000000000..797bfb6d62
--- /dev/null
+++ b/Documentation/config/revert.txt
@@ -0,0 +1,3 @@
+revert.reference::
+	Setting this variable to true makes `git revert` to behave
+	as if the `--reference` option is given.
diff --git a/Documentation/git-revert.txt b/Documentation/git-revert.txt
index bb92a4a451..8463fe9cf7 100644
--- a/Documentation/git-revert.txt
+++ b/Documentation/git-revert.txt
@@ -117,6 +117,15 @@ effect to your index in a row.
 	Allow the rerere mechanism to update the index with the
 	result of auto-conflict resolution if possible.
 
+--reference::
+	Instead of starting the body of the log message with "This
+	reverts <full object name of the commit being reverted>.",
+	refer to the commit using "--pretty=reference" format
+	(cf. linkgit:git-log[1]).  The `revert.reference`
+	configuration variable can be used to enable this option by
+	default.
+
+
 SEQUENCER SUBCOMMANDS
 ---------------------
 include::sequencer.txt[]
diff --git a/builtin/revert.c b/builtin/revert.c
index 51776abea6..ada51e46b9 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -116,6 +116,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 			N_("option for merge strategy"), option_parse_x),
 		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
 		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+		OPT_BOOL(0, "reference", &opts->commit_use_reference,
+			 N_("use the 'reference' format to refer to commits")),
 		OPT_END()
 	};
 	struct option *options = base_options;
diff --git a/sequencer.c b/sequencer.c
index a5f678f452..96fec6ef6d 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -221,6 +221,9 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
 		return ret;
 	}
 
+	if (!strcmp(k, "revert.reference"))
+		opts->commit_use_reference = git_config_bool(k, v);
+
 	status = git_gpg_config(k, v, NULL);
 	if (status)
 		return status;
@@ -2059,6 +2062,20 @@ static int should_edit(struct replay_opts *opts) {
 	return opts->edit;
 }
 
+static void refer_to_commit(struct replay_opts *opts,
+			    struct strbuf *msgbuf, struct commit *commit)
+{
+	if (opts->commit_use_reference) {
+		struct pretty_print_context ctx = {
+			.abbrev = DEFAULT_ABBREV,
+			.date_mode.type = DATE_SHORT,
+		};
+		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);
+	} else {
+		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
+	}
+}
+
 static int do_pick_commit(struct repository *r,
 			  struct todo_item *item,
 			  struct replay_opts *opts,
@@ -2167,14 +2184,20 @@ static int do_pick_commit(struct repository *r,
 		base_label = msg.label;
 		next = parent;
 		next_label = msg.parent_label;
-		strbuf_addstr(&msgbuf, "Revert \"");
-		strbuf_addstr(&msgbuf, msg.subject);
-		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
-		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
+		if (opts->commit_use_reference) {
+			strbuf_addstr(&msgbuf,
+				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
+		} else {
+			strbuf_addstr(&msgbuf, "Revert \"");
+			strbuf_addstr(&msgbuf, msg.subject);
+			strbuf_addstr(&msgbuf, "\"");
+		}
+		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
+		refer_to_commit(opts, &msgbuf, commit);
 
 		if (commit->parents && commit->parents->next) {
 			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
-			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
+			refer_to_commit(opts, &msgbuf, parent);
 		}
 		strbuf_addstr(&msgbuf, ".\n");
 	} else {
diff --git a/sequencer.h b/sequencer.h
index da64473636..698599fe4e 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -49,6 +49,7 @@ struct replay_opts {
 	int reschedule_failed_exec;
 	int committer_date_is_author_date;
 	int ignore_date;
+	int commit_use_reference;
 
 	int mainline;
 
diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
index 8617efaaf1..a386ae9e88 100755
--- a/t/t3501-revert-cherry-pick.sh
+++ b/t/t3501-revert-cherry-pick.sh
@@ -159,6 +159,7 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
 '
 
 test_expect_success 'advice from failed revert' '
+	test_when_finished "git reset --hard" &&
 	test_commit --no-tag "add dream" dream dream &&
 	dream_oid=$(git rev-parse --short HEAD) &&
 	cat <<-EOF >expected &&
@@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
 	test_must_fail git revert HEAD^ 2>actual &&
 	test_cmp expected actual
 '
+
+test_expect_success 'identification of reverted commit (default)' '
+	test_commit to-ident &&
+	test_when_finished "git reset --hard to-ident" &&
+	git checkout --detach to-ident &&
+	git revert --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'identification of reverted commit (--reference)' '
+	git checkout --detach to-ident &&
+	git revert --reference --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'identification of reverted commit (revert.reference)' '
+	git checkout --detach to-ident &&
+	git -c revert.reference=true revert --no-edit HEAD &&
+	git cat-file commit HEAD >actual.raw &&
+	grep "^This reverts " actual.raw >actual &&
+	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
+	test_cmp expect actual
+'
+
 test_done
-- 
2.36.1-331-g1b5d92e060


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v3] revert: optionally refer to commit in the "reference" format
  2022-05-27  6:01     ` [PATCH v3] " Junio C Hamano
@ 2022-05-30 16:40       ` Johannes Schindelin
  2022-05-31 14:00       ` Phillip Wood
  2022-06-01 15:14       ` Ævar Arnfjörð Bjarmason
  2 siblings, 0 replies; 20+ messages in thread
From: Johannes Schindelin @ 2022-05-30 16:40 UTC (permalink / raw)
  To: Junio C Hamano; +Cc: git, Phillip Wood, Ævar Arnfjörð Bjarmason

Hi Junio,

On Thu, 26 May 2022, Junio C Hamano wrote:

> A typical "git revert" commit uses the full title of the original
> commit in its title, and starts its body of the message with:
>
>     This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.
>
> This does not encourage the best practice of describing not just
> "what" (i.e. "Revert X" on the title says what we did) but "why"
> (i.e. and it does not say why X was undesirable).
>
> We can instead phrase this first line of the body to be more like
>
>     This reverts commit 8fa7f667 (do this and that, 2022-04-25)
>
> so that the title does not have to be
>
>     Revert "do this and that"
>
> We can instead use the title to describe "why" we are reverting the
> original commit.
>
> Introduce the "--reference" option to "git revert", and also the
> revert.reference configuration variable, which defaults to false, to
> tweak the title and the first line of the draft commit message for
> when creating a "revert" commit.
>
> When this option is in use, the first line of the pre-filled editor
> buffer becomes a comment line that tells the user to say _why_.  If
> the user exits the editor without touching this line by mistake,
> what we prepare to become the first line of the body, i.e. "This
> reverts commit 8fa7f667 (do this and that, 2022-04-25)", ends up to
> be the title of the resulting commit.  This behaviour is designed to
> help such a user to identify such a revert in "git log --oneline"
> easily so that it can be further reworded with "git rebase -i" later.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>
>  * The only difference since the second one is that the first line of
>    the log message template is commented out and has asterisks to
>    draw more attention.  The last paragraph (new) in the proposed
>    log message explains the rationale behind this design.

While it may be more purist to try to force the user to provide a
description by having a non-comment placeholder there, from my experience
with PullRequest/Issue templates convinces me that the comment is the more
practical approach.

Looking good,
Dscho

>
>    Third-time a charm, hopefully.
>
> Range-diff against v2:
> 1:  4152fc2092 ! 1:  f4325a503a revert: optionally refer to commit in the "reference" format
>     @@ Commit message
>          tweak the title and the first line of the draft commit message for
>          when creating a "revert" commit.
>
>     +    When this option is in use, the first line of the pre-filled editor
>     +    buffer becomes a comment line that tells the user to say _why_.  If
>     +    the user exits the editor without touching this line by mistake,
>     +    what we prepare to become the first line of the body, i.e. "This
>     +    reverts commit 8fa7f667 (do this and that, 2022-04-25)", ends up to
>     +    be the title of the resulting commit.  This behaviour is designed to
>     +    help such a user to identify such a revert in "git log --oneline"
>     +    easily so that it can be further reworded with "git rebase -i" later.
>     +
>          Signed-off-by: Junio C Hamano <gitster@pobox.com>
>
>       ## Documentation/config/revert.txt (new) ##
>     @@ sequencer.c: static int do_pick_commit(struct repository *r,
>      -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
>      -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
>      +		if (opts->commit_use_reference) {
>     -+			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
>     ++			strbuf_addstr(&msgbuf,
>     ++				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
>      +		} else {
>      +			strbuf_addstr(&msgbuf, "Revert \"");
>      +			strbuf_addstr(&msgbuf, msg.subject);
>
>  Documentation/config/revert.txt |  3 +++
>  Documentation/git-revert.txt    |  9 +++++++++
>  builtin/revert.c                |  2 ++
>  sequencer.c                     | 33 ++++++++++++++++++++++++++++-----
>  sequencer.h                     |  1 +
>  t/t3501-revert-cherry-pick.sh   | 31 +++++++++++++++++++++++++++++++
>  6 files changed, 74 insertions(+), 5 deletions(-)
>  create mode 100644 Documentation/config/revert.txt
>
> diff --git a/Documentation/config/revert.txt b/Documentation/config/revert.txt
> new file mode 100644
> index 0000000000..797bfb6d62
> --- /dev/null
> +++ b/Documentation/config/revert.txt
> @@ -0,0 +1,3 @@
> +revert.reference::
> +	Setting this variable to true makes `git revert` to behave
> +	as if the `--reference` option is given.
> diff --git a/Documentation/git-revert.txt b/Documentation/git-revert.txt
> index bb92a4a451..8463fe9cf7 100644
> --- a/Documentation/git-revert.txt
> +++ b/Documentation/git-revert.txt
> @@ -117,6 +117,15 @@ effect to your index in a row.
>  	Allow the rerere mechanism to update the index with the
>  	result of auto-conflict resolution if possible.
>
> +--reference::
> +	Instead of starting the body of the log message with "This
> +	reverts <full object name of the commit being reverted>.",
> +	refer to the commit using "--pretty=reference" format
> +	(cf. linkgit:git-log[1]).  The `revert.reference`
> +	configuration variable can be used to enable this option by
> +	default.
> +
> +
>  SEQUENCER SUBCOMMANDS
>  ---------------------
>  include::sequencer.txt[]
> diff --git a/builtin/revert.c b/builtin/revert.c
> index 51776abea6..ada51e46b9 100644
> --- a/builtin/revert.c
> +++ b/builtin/revert.c
> @@ -116,6 +116,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
>  			N_("option for merge strategy"), option_parse_x),
>  		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
>  		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
> +		OPT_BOOL(0, "reference", &opts->commit_use_reference,
> +			 N_("use the 'reference' format to refer to commits")),
>  		OPT_END()
>  	};
>  	struct option *options = base_options;
> diff --git a/sequencer.c b/sequencer.c
> index a5f678f452..96fec6ef6d 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -221,6 +221,9 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
>  		return ret;
>  	}
>
> +	if (!strcmp(k, "revert.reference"))
> +		opts->commit_use_reference = git_config_bool(k, v);
> +
>  	status = git_gpg_config(k, v, NULL);
>  	if (status)
>  		return status;
> @@ -2059,6 +2062,20 @@ static int should_edit(struct replay_opts *opts) {
>  	return opts->edit;
>  }
>
> +static void refer_to_commit(struct replay_opts *opts,
> +			    struct strbuf *msgbuf, struct commit *commit)
> +{
> +	if (opts->commit_use_reference) {
> +		struct pretty_print_context ctx = {
> +			.abbrev = DEFAULT_ABBREV,
> +			.date_mode.type = DATE_SHORT,
> +		};
> +		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);
> +	} else {
> +		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
> +	}
> +}
> +
>  static int do_pick_commit(struct repository *r,
>  			  struct todo_item *item,
>  			  struct replay_opts *opts,
> @@ -2167,14 +2184,20 @@ static int do_pick_commit(struct repository *r,
>  		base_label = msg.label;
>  		next = parent;
>  		next_label = msg.parent_label;
> -		strbuf_addstr(&msgbuf, "Revert \"");
> -		strbuf_addstr(&msgbuf, msg.subject);
> -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
> -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> +		if (opts->commit_use_reference) {
> +			strbuf_addstr(&msgbuf,
> +				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
> +		} else {
> +			strbuf_addstr(&msgbuf, "Revert \"");
> +			strbuf_addstr(&msgbuf, msg.subject);
> +			strbuf_addstr(&msgbuf, "\"");
> +		}
> +		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
> +		refer_to_commit(opts, &msgbuf, commit);
>
>  		if (commit->parents && commit->parents->next) {
>  			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
> -			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
> +			refer_to_commit(opts, &msgbuf, parent);
>  		}
>  		strbuf_addstr(&msgbuf, ".\n");
>  	} else {
> diff --git a/sequencer.h b/sequencer.h
> index da64473636..698599fe4e 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -49,6 +49,7 @@ struct replay_opts {
>  	int reschedule_failed_exec;
>  	int committer_date_is_author_date;
>  	int ignore_date;
> +	int commit_use_reference;
>
>  	int mainline;
>
> diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
> index 8617efaaf1..a386ae9e88 100755
> --- a/t/t3501-revert-cherry-pick.sh
> +++ b/t/t3501-revert-cherry-pick.sh
> @@ -159,6 +159,7 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
>  '
>
>  test_expect_success 'advice from failed revert' '
> +	test_when_finished "git reset --hard" &&
>  	test_commit --no-tag "add dream" dream dream &&
>  	dream_oid=$(git rev-parse --short HEAD) &&
>  	cat <<-EOF >expected &&
> @@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
>  	test_must_fail git revert HEAD^ 2>actual &&
>  	test_cmp expected actual
>  '
> +
> +test_expect_success 'identification of reverted commit (default)' '
> +	test_commit to-ident &&
> +	test_when_finished "git reset --hard to-ident" &&
> +	git checkout --detach to-ident &&
> +	git revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (--reference)' '
> +	git checkout --detach to-ident &&
> +	git revert --reference --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (revert.reference)' '
> +	git checkout --detach to-ident &&
> +	git -c revert.reference=true revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
>  test_done
> --
> 2.36.1-331-g1b5d92e060
>
>

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Side effects in Git's test suite, was Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-23 22:48   ` Junio C Hamano
  2022-05-27  6:01     ` [PATCH v3] " Junio C Hamano
@ 2022-05-30 16:50     ` Johannes Schindelin
  2022-05-31  8:03       ` Ævar Arnfjörð Bjarmason
  1 sibling, 1 reply; 20+ messages in thread
From: Johannes Schindelin @ 2022-05-30 16:50 UTC (permalink / raw)
  To: Junio C Hamano; +Cc: git

Hi Junio,

On Mon, 23 May 2022, Junio C Hamano wrote:

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>
> >> +test_expect_success 'identification of reverted commit (reference)' '
> >> +	git checkout --detach to-ident &&
> >> +	git revert --reference --no-edit HEAD &&
> >> +	git cat-file commit HEAD >actual.raw &&
> >> +	grep "^This reverts " actual.raw >actual &&
> >> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> >> +	test_cmp expect actual
> >> +'
> >
> > If it was up to me, I would combine these three test cases, if only to
> > help the `--run=<single-number>` case (the latter two depend on the
> > side effect of the first one to create a `to-ident` tag).
>
> I wonder if our prereq infrastructure is lightweight and scalable enough
> so that we can easily add a support a pseudo-prerequisite PREVIOUS that
> lets us say
>
> 	test_expect_success PREVIOUS "identification ..." '
> 		...
> 	'
>
> to mean that this test requires the previous test has not been
> skipped.

In theory, this sounds good to me.

In practice, however, side effects are awful and make everything harder,
from developing code to debugging to helping new contributors. I wish we
would do away with them altogether and have something more akin to the
before/after constructs known from e.g. TestNG (think `@BeforeTest` and
`@BeforeClass`).

One option would be to mark `setup` steps completely differently, sort of
imitating the prereq infrastructure instead of using
`test_expect_success`. Kind of prereqs, but required to pass.

This could potentially allow us to randomize the order in which the test
cases are run, to identify and fix (unintended) side effects.

A complication is that we have nothing in the way of `@AfterClass`, i.e.
we do not have a way to, say, run an Apache instance for the lifecycle of
a given test script _and tear it down at the end_.

Another, rather obvious complication is that we have 17 years of commit
history introducing side effects left and right :laughing:

Ciao,
Dscho

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: Side effects in Git's test suite, was Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-30 16:50     ` Side effects in Git's test suite, was Re: [PATCH] " Johannes Schindelin
@ 2022-05-31  8:03       ` Ævar Arnfjörð Bjarmason
  0 siblings, 0 replies; 20+ messages in thread
From: Ævar Arnfjörð Bjarmason @ 2022-05-31  8:03 UTC (permalink / raw)
  To: Johannes Schindelin; +Cc: Junio C Hamano, git


On Mon, May 30 2022, Johannes Schindelin wrote:

> Hi Junio,
>
> On Mon, 23 May 2022, Junio C Hamano wrote:
>
>> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>>
>> >> +test_expect_success 'identification of reverted commit (reference)' '
>> >> +	git checkout --detach to-ident &&
>> >> +	git revert --reference --no-edit HEAD &&
>> >> +	git cat-file commit HEAD >actual.raw &&
>> >> +	grep "^This reverts " actual.raw >actual &&
>> >> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
>> >> +	test_cmp expect actual
>> >> +'
>> >
>> > If it was up to me, I would combine these three test cases, if only to
>> > help the `--run=<single-number>` case (the latter two depend on the
>> > side effect of the first one to create a `to-ident` tag).
>>
>> I wonder if our prereq infrastructure is lightweight and scalable enough
>> so that we can easily add a support a pseudo-prerequisite PREVIOUS that
>> lets us say
>>
>> 	test_expect_success PREVIOUS "identification ..." '
>> 		...
>> 	'
>>
>> to mean that this test requires the previous test has not been
>> skipped.
>
> In theory, this sounds good to me.
>
> In practice, however, side effects are awful and make everything harder,
> from developing code to debugging to helping new contributors. I wish we
> would do away with them altogether and have something more akin to the
> before/after constructs known from e.g. TestNG (think `@BeforeTest` and
> `@BeforeClass`).
>
> One option would be to mark `setup` steps completely differently, sort of
> imitating the prereq infrastructure instead of using
> `test_expect_success`. Kind of prereqs, but required to pass.

I've suggested a test_expect_setup before:
https://lore.kernel.org/git/8735vrvg39.fsf@evledraar.gmail.com/;
basically a test_expect_success that ignores GIT_SKIP_TESTS and --run.

I think that even if we could imagine much more complex relationships
(up to and including writing these tests as Makefiles instead) it's
better to just have the simpler "this is a setup".

Then for everything more complex be more eager to split up tests.

> This could potentially allow us to randomize the order in which the test
> cases are run, to identify and fix (unintended) side effects.

Yes, a "chaos monkey" mode similar to --stress would be nice.

> A complication is that we have nothing in the way of `@AfterClass`, i.e.
> we do not have a way to, say, run an Apache instance for the lifecycle of
> a given test script _and tear it down at the end_.

I think this is generally a feature in that if you find yourself needing
this you should split the test up so that the Apache setup is in only
one file.

E.g. in the case of some http tests we have a prereq on something for
git:// and a different thing (apache) for http:// tests, so that
depending on what combination you have we might end up needlessly
skipping tests.

> Another, rather obvious complication is that we have 17 years of commit
> history introducing side effects left and right :laughing:


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v3] revert: optionally refer to commit in the "reference" format
  2022-05-27  6:01     ` [PATCH v3] " Junio C Hamano
  2022-05-30 16:40       ` Johannes Schindelin
@ 2022-05-31 14:00       ` Phillip Wood
  2022-06-01  4:45         ` Junio C Hamano
  2022-06-01 15:14       ` Ævar Arnfjörð Bjarmason
  2 siblings, 1 reply; 20+ messages in thread
From: Phillip Wood @ 2022-05-31 14:00 UTC (permalink / raw)
  To: Junio C Hamano, git
  Cc: Johannes Schindelin, Phillip Wood,
	Ævar Arnfjörð Bjarmason

Hi Junio

On 27/05/2022 07:01, Junio C Hamano wrote:
> A typical "git revert" commit uses the full title of the original
> commit in its title, and starts its body of the message with:
> 
>      This reverts commit 8fa7f667cf61386257c00d6e954855cc3215ae91.
> 
> This does not encourage the best practice of describing not just
> "what" (i.e. "Revert X" on the title says what we did) but "why"
> (i.e. and it does not say why X was undesirable).
> 
> We can instead phrase this first line of the body to be more like
> 
>      This reverts commit 8fa7f667 (do this and that, 2022-04-25)
> 
> so that the title does not have to be
> 
>      Revert "do this and that"
> 
> We can instead use the title to describe "why" we are reverting the
> original commit.
> 
> Introduce the "--reference" option to "git revert", and also the
> revert.reference configuration variable, which defaults to false, to
> tweak the title and the first line of the draft commit message for
> when creating a "revert" commit.
> 
> When this option is in use, the first line of the pre-filled editor
> buffer becomes a comment line that tells the user to say _why_.  If
> the user exits the editor without touching this line by mistake,
> what we prepare to become the first line of the body, i.e. "This
> reverts commit 8fa7f667 (do this and that, 2022-04-25)", ends up to
> be the title of the resulting commit.  This behaviour is designed to
> help such a user to identify such a revert in "git log --oneline"
> easily so that it can be further reworded with "git rebase -i" later.
> 
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
> 
>   * The only difference since the second one is that the first line of
>     the log message template is commented out and has asterisks to
>     draw more attention.  The last paragraph (new) in the proposed
>     log message explains the rationale behind this design.
> 
>     Third-time a charm, hopefully.

I think the changes to the template message are good. We're still adding 
"--reference" as a valid option to cherry-pick though which I don't 
think is a good idea (though in the future we may want to allow 
"cherry-pick -x --reference")

Best Wishes

Phillip

> Range-diff against v2:
> 1:  4152fc2092 ! 1:  f4325a503a revert: optionally refer to commit in the "reference" format
>      @@ Commit message
>           tweak the title and the first line of the draft commit message for
>           when creating a "revert" commit.
>       
>      +    When this option is in use, the first line of the pre-filled editor
>      +    buffer becomes a comment line that tells the user to say _why_.  If
>      +    the user exits the editor without touching this line by mistake,
>      +    what we prepare to become the first line of the body, i.e. "This
>      +    reverts commit 8fa7f667 (do this and that, 2022-04-25)", ends up to
>      +    be the title of the resulting commit.  This behaviour is designed to
>      +    help such a user to identify such a revert in "git log --oneline"
>      +    easily so that it can be further reworded with "git rebase -i" later.
>      +
>           Signed-off-by: Junio C Hamano <gitster@pobox.com>
>       
>        ## Documentation/config/revert.txt (new) ##
>      @@ sequencer.c: static int do_pick_commit(struct repository *r,
>       -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
>       -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
>       +		if (opts->commit_use_reference) {
>      -+			strbuf_addstr(&msgbuf, "DESCRIBE WHY WE ARE REVERTING HERE");
>      ++			strbuf_addstr(&msgbuf,
>      ++				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
>       +		} else {
>       +			strbuf_addstr(&msgbuf, "Revert \"");
>       +			strbuf_addstr(&msgbuf, msg.subject);
> 
>   Documentation/config/revert.txt |  3 +++
>   Documentation/git-revert.txt    |  9 +++++++++
>   builtin/revert.c                |  2 ++
>   sequencer.c                     | 33 ++++++++++++++++++++++++++++-----
>   sequencer.h                     |  1 +
>   t/t3501-revert-cherry-pick.sh   | 31 +++++++++++++++++++++++++++++++
>   6 files changed, 74 insertions(+), 5 deletions(-)
>   create mode 100644 Documentation/config/revert.txt
> 
> diff --git a/Documentation/config/revert.txt b/Documentation/config/revert.txt
> new file mode 100644
> index 0000000000..797bfb6d62
> --- /dev/null
> +++ b/Documentation/config/revert.txt
> @@ -0,0 +1,3 @@
> +revert.reference::
> +	Setting this variable to true makes `git revert` to behave
> +	as if the `--reference` option is given.
> diff --git a/Documentation/git-revert.txt b/Documentation/git-revert.txt
> index bb92a4a451..8463fe9cf7 100644
> --- a/Documentation/git-revert.txt
> +++ b/Documentation/git-revert.txt
> @@ -117,6 +117,15 @@ effect to your index in a row.
>   	Allow the rerere mechanism to update the index with the
>   	result of auto-conflict resolution if possible.
>   
> +--reference::
> +	Instead of starting the body of the log message with "This
> +	reverts <full object name of the commit being reverted>.",
> +	refer to the commit using "--pretty=reference" format
> +	(cf. linkgit:git-log[1]).  The `revert.reference`
> +	configuration variable can be used to enable this option by
> +	default.
> +
> +
>   SEQUENCER SUBCOMMANDS
>   ---------------------
>   include::sequencer.txt[]
> diff --git a/builtin/revert.c b/builtin/revert.c
> index 51776abea6..ada51e46b9 100644
> --- a/builtin/revert.c
> +++ b/builtin/revert.c
> @@ -116,6 +116,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
>   			N_("option for merge strategy"), option_parse_x),
>   		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
>   		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
> +		OPT_BOOL(0, "reference", &opts->commit_use_reference,
> +			 N_("use the 'reference' format to refer to commits")),
>   		OPT_END()
>   	};
>   	struct option *options = base_options;
> diff --git a/sequencer.c b/sequencer.c
> index a5f678f452..96fec6ef6d 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -221,6 +221,9 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
>   		return ret;
>   	}
>   
> +	if (!strcmp(k, "revert.reference"))
> +		opts->commit_use_reference = git_config_bool(k, v);
> +
>   	status = git_gpg_config(k, v, NULL);
>   	if (status)
>   		return status;
> @@ -2059,6 +2062,20 @@ static int should_edit(struct replay_opts *opts) {
>   	return opts->edit;
>   }
>   
> +static void refer_to_commit(struct replay_opts *opts,
> +			    struct strbuf *msgbuf, struct commit *commit)
> +{
> +	if (opts->commit_use_reference) {
> +		struct pretty_print_context ctx = {
> +			.abbrev = DEFAULT_ABBREV,
> +			.date_mode.type = DATE_SHORT,
> +		};
> +		format_commit_message(commit, "%h (%s, %ad)", msgbuf, &ctx);
> +	} else {
> +		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
> +	}
> +}
> +
>   static int do_pick_commit(struct repository *r,
>   			  struct todo_item *item,
>   			  struct replay_opts *opts,
> @@ -2167,14 +2184,20 @@ static int do_pick_commit(struct repository *r,
>   		base_label = msg.label;
>   		next = parent;
>   		next_label = msg.parent_label;
> -		strbuf_addstr(&msgbuf, "Revert \"");
> -		strbuf_addstr(&msgbuf, msg.subject);
> -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
> -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> +		if (opts->commit_use_reference) {
> +			strbuf_addstr(&msgbuf,
> +				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
> +		} else {
> +			strbuf_addstr(&msgbuf, "Revert \"");
> +			strbuf_addstr(&msgbuf, msg.subject);
> +			strbuf_addstr(&msgbuf, "\"");
> +		}
> +		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
> +		refer_to_commit(opts, &msgbuf, commit);
>   
>   		if (commit->parents && commit->parents->next) {
>   			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
> -			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
> +			refer_to_commit(opts, &msgbuf, parent);
>   		}
>   		strbuf_addstr(&msgbuf, ".\n");
>   	} else {
> diff --git a/sequencer.h b/sequencer.h
> index da64473636..698599fe4e 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -49,6 +49,7 @@ struct replay_opts {
>   	int reschedule_failed_exec;
>   	int committer_date_is_author_date;
>   	int ignore_date;
> +	int commit_use_reference;
>   
>   	int mainline;
>   
> diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
> index 8617efaaf1..a386ae9e88 100755
> --- a/t/t3501-revert-cherry-pick.sh
> +++ b/t/t3501-revert-cherry-pick.sh
> @@ -159,6 +159,7 @@ test_expect_success 'cherry-pick works with dirty renamed file' '
>   '
>   
>   test_expect_success 'advice from failed revert' '
> +	test_when_finished "git reset --hard" &&
>   	test_commit --no-tag "add dream" dream dream &&
>   	dream_oid=$(git rev-parse --short HEAD) &&
>   	cat <<-EOF >expected &&
> @@ -174,4 +175,34 @@ test_expect_success 'advice from failed revert' '
>   	test_must_fail git revert HEAD^ 2>actual &&
>   	test_cmp expected actual
>   '
> +
> +test_expect_success 'identification of reverted commit (default)' '
> +	test_commit to-ident &&
> +	test_when_finished "git reset --hard to-ident" &&
> +	git checkout --detach to-ident &&
> +	git revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (--reference)' '
> +	git checkout --detach to-ident &&
> +	git revert --reference --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (revert.reference)' '
> +	git checkout --detach to-ident &&
> +	git -c revert.reference=true revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
>   test_done

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v3] revert: optionally refer to commit in the "reference" format
  2022-05-31 14:00       ` Phillip Wood
@ 2022-06-01  4:45         ` Junio C Hamano
  2022-06-01 15:03           ` Phillip Wood
  0 siblings, 1 reply; 20+ messages in thread
From: Junio C Hamano @ 2022-06-01  4:45 UTC (permalink / raw)
  To: Phillip Wood
  Cc: git, Johannes Schindelin, Phillip Wood,
	Ævar Arnfjörð Bjarmason

Phillip Wood <phillip.wood123@gmail.com> writes:

> I think the changes to the template message are good. We're still
> adding "--reference" as a valid option to cherry-pick though which I
> don't think is a good idea (though in the future we may want to allow 
> "cherry-pick -x --reference")

I love when people notice mistakes that the original author and
other people missed, many eyes making all bugs shallow.

I am inclined to apply the following on top.  How does it look?

Thanks.

----- >8 --------- >8 --------- >8 --------- >8 -----
Subject: [PATCH] revert: --reference should apply only to 'revert', not 'cherry-pick'

As 'revert' and 'cherry-pick' share a lot of code, it is easy to
modify the behaviour of one command and inadvertently affect the
other.  An earlier change to teach the '--reference' option and the
'revert.reference' configuration variable to the former was not
careful enough and 'cherry-pick --reference' wasn't rejected as an
error.

It is possible to think 'cherry-pick -x' might benefit from the
'--reference' option, but it is fundamentally different from
'revert' in at least two ways to make it questionable:

 - 'revert' names a commit that is ancestor of the resulting commit,
   so an abbreviated object name with human readable title is
   sufficient to identify the named commit uniquely without using
   the full object name.  On the other hand, 'cherry-pick'
   usually [*] picks a commit that is not an ancestor.  It might be
   even picking a private commit that never becomes part of the
   public history.

 - The whole commit message of 'cherry-pick' is a copy of the
   original commit, and there is nothing gained to repeat only the
   title part on 'cherry-picked from' message.

[*] well, you could revert and then you can pick the original that
    was reverted to get back to where you were, but then you can
    revert the revert to do the same thing.

Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/revert.c              | 9 +++++++--
 sequencer.c                   | 2 +-
 t/t3501-revert-cherry-pick.sh | 6 ++++++
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/builtin/revert.c b/builtin/revert.c
index ada51e46b9..f84c253f4c 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -116,8 +116,6 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 			N_("option for merge strategy"), option_parse_x),
 		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
 		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
-		OPT_BOOL(0, "reference", &opts->commit_use_reference,
-			 N_("use the 'reference' format to refer to commits")),
 		OPT_END()
 	};
 	struct option *options = base_options;
@@ -132,6 +130,13 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 			OPT_END(),
 		};
 		options = parse_options_concat(options, cp_extra);
+	} else if (opts->action == REPLAY_REVERT) {
+		struct option cp_extra[] = {
+			OPT_BOOL(0, "reference", &opts->commit_use_reference,
+				 N_("use the 'reference' format to refer to commits")),
+			OPT_END(),
+		};
+		options = parse_options_concat(options, cp_extra);
 	}
 
 	argc = parse_options(argc, argv, NULL, options, usage_str,
diff --git a/sequencer.c b/sequencer.c
index 96fec6ef6d..4b66a1f79c 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -221,7 +221,7 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
 		return ret;
 	}
 
-	if (!strcmp(k, "revert.reference"))
+	if (opts->action == REPLAY_REVERT && !strcmp(k, "revert.reference"))
 		opts->commit_use_reference = git_config_bool(k, v);
 
 	status = git_gpg_config(k, v, NULL);
diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
index a386ae9e88..fb4466599b 100755
--- a/t/t3501-revert-cherry-pick.sh
+++ b/t/t3501-revert-cherry-pick.sh
@@ -205,4 +205,10 @@ test_expect_success 'identification of reverted commit (revert.reference)' '
 	test_cmp expect actual
 '
 
+test_expect_success 'cherry-pick is unaware of --reference (for now)' '
+	test_when_finished "git reset --hard" &&
+	test_must_fail git cherry-pick --reference HEAD 2>actual &&
+	grep "^usage: git cherry-pick" actual
+'
+
 test_done
-- 
2.36.1-393-g8f55ede6c2


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v3] revert: optionally refer to commit in the "reference" format
  2022-06-01  4:45         ` Junio C Hamano
@ 2022-06-01 15:03           ` Phillip Wood
  0 siblings, 0 replies; 20+ messages in thread
From: Phillip Wood @ 2022-06-01 15:03 UTC (permalink / raw)
  To: Junio C Hamano
  Cc: git, Johannes Schindelin, Phillip Wood,
	Ævar Arnfjörð Bjarmason

Hi Junio

On 01/06/2022 05:45, Junio C Hamano wrote:
> Phillip Wood <phillip.wood123@gmail.com> writes:
> 
>> I think the changes to the template message are good. We're still
>> adding "--reference" as a valid option to cherry-pick though which I
>> don't think is a good idea (though in the future we may want to allow
>> "cherry-pick -x --reference")
> 
> I love when people notice mistakes that the original author and
> other people missed, many eyes making all bugs shallow.
> 
> I am inclined to apply the following on top.  How does it look?

It looks good to me.

Best Wishes

Phillip

> Thanks.
> 
> ----- >8 --------- >8 --------- >8 --------- >8 -----
> Subject: [PATCH] revert: --reference should apply only to 'revert', not 'cherry-pick'
> 
> As 'revert' and 'cherry-pick' share a lot of code, it is easy to
> modify the behaviour of one command and inadvertently affect the
> other.  An earlier change to teach the '--reference' option and the
> 'revert.reference' configuration variable to the former was not
> careful enough and 'cherry-pick --reference' wasn't rejected as an
> error.
> 
> It is possible to think 'cherry-pick -x' might benefit from the
> '--reference' option, but it is fundamentally different from
> 'revert' in at least two ways to make it questionable:
> 
>   - 'revert' names a commit that is ancestor of the resulting commit,
>     so an abbreviated object name with human readable title is
>     sufficient to identify the named commit uniquely without using
>     the full object name.  On the other hand, 'cherry-pick'
>     usually [*] picks a commit that is not an ancestor.  It might be
>     even picking a private commit that never becomes part of the
>     public history.
> 
>   - The whole commit message of 'cherry-pick' is a copy of the
>     original commit, and there is nothing gained to repeat only the
>     title part on 'cherry-picked from' message.
> 
> [*] well, you could revert and then you can pick the original that
>      was reverted to get back to where you were, but then you can
>      revert the revert to do the same thing.
> 
> Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>   builtin/revert.c              | 9 +++++++--
>   sequencer.c                   | 2 +-
>   t/t3501-revert-cherry-pick.sh | 6 ++++++
>   3 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/builtin/revert.c b/builtin/revert.c
> index ada51e46b9..f84c253f4c 100644
> --- a/builtin/revert.c
> +++ b/builtin/revert.c
> @@ -116,8 +116,6 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
>   			N_("option for merge strategy"), option_parse_x),
>   		{ OPTION_STRING, 'S', "gpg-sign", &opts->gpg_sign, N_("key-id"),
>   		  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
> -		OPT_BOOL(0, "reference", &opts->commit_use_reference,
> -			 N_("use the 'reference' format to refer to commits")),
>   		OPT_END()
>   	};
>   	struct option *options = base_options;
> @@ -132,6 +130,13 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
>   			OPT_END(),
>   		};
>   		options = parse_options_concat(options, cp_extra);
> +	} else if (opts->action == REPLAY_REVERT) {
> +		struct option cp_extra[] = {
> +			OPT_BOOL(0, "reference", &opts->commit_use_reference,
> +				 N_("use the 'reference' format to refer to commits")),
> +			OPT_END(),
> +		};
> +		options = parse_options_concat(options, cp_extra);
>   	}
>   
>   	argc = parse_options(argc, argv, NULL, options, usage_str,
> diff --git a/sequencer.c b/sequencer.c
> index 96fec6ef6d..4b66a1f79c 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -221,7 +221,7 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
>   		return ret;
>   	}
>   
> -	if (!strcmp(k, "revert.reference"))
> +	if (opts->action == REPLAY_REVERT && !strcmp(k, "revert.reference"))
>   		opts->commit_use_reference = git_config_bool(k, v);
>   
>   	status = git_gpg_config(k, v, NULL);
> diff --git a/t/t3501-revert-cherry-pick.sh b/t/t3501-revert-cherry-pick.sh
> index a386ae9e88..fb4466599b 100755
> --- a/t/t3501-revert-cherry-pick.sh
> +++ b/t/t3501-revert-cherry-pick.sh
> @@ -205,4 +205,10 @@ test_expect_success 'identification of reverted commit (revert.reference)' '
>   	test_cmp expect actual
>   '
>   
> +test_expect_success 'cherry-pick is unaware of --reference (for now)' '
> +	test_when_finished "git reset --hard" &&
> +	test_must_fail git cherry-pick --reference HEAD 2>actual &&
> +	grep "^usage: git cherry-pick" actual
> +'
> +
>   test_done

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v3] revert: optionally refer to commit in the "reference" format
  2022-05-27  6:01     ` [PATCH v3] " Junio C Hamano
  2022-05-30 16:40       ` Johannes Schindelin
  2022-05-31 14:00       ` Phillip Wood
@ 2022-06-01 15:14       ` Ævar Arnfjörð Bjarmason
  2022-06-01 21:52         ` Junio C Hamano
  2 siblings, 1 reply; 20+ messages in thread
From: Ævar Arnfjörð Bjarmason @ 2022-06-01 15:14 UTC (permalink / raw)
  To: Junio C Hamano; +Cc: git, Johannes Schindelin, Phillip Wood


On Thu, May 26 2022, Junio C Hamano wrote:

> When this option is in use, the first line of the pre-filled editor
> buffer becomes a comment line that tells the user to say _why_.  If
> the user exits the editor without touching this line by mistake,
> what we prepare to become the first line of the body, i.e. "This
> reverts commit 8fa7f667 (do this and that, 2022-04-25)", ends up to
> be the title of the resulting commit.  This behaviour is designed to
> help such a user to identify such a revert in "git log --oneline"
> easily so that it can be further reworded with "git rebase -i" later.

This is a good trade-off, and means that the --no-edit case is also
preserved. However...

> @@ -2167,14 +2184,20 @@ static int do_pick_commit(struct repository *r,
>  		base_label = msg.label;
>  		next = parent;
>  		next_label = msg.parent_label;
> -		strbuf_addstr(&msgbuf, "Revert \"");
> -		strbuf_addstr(&msgbuf, msg.subject);
> -		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
> -		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
> +		if (opts->commit_use_reference) {
> +			strbuf_addstr(&msgbuf,
> +				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
> +		} else {
> +			strbuf_addstr(&msgbuf, "Revert \"");
> +			strbuf_addstr(&msgbuf, msg.subject);
> +			strbuf_addstr(&msgbuf, "\"");
> +		}
> +		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
> +		refer_to_commit(opts, &msgbuf, commit);
>  
>  		if (commit->parents && commit->parents->next) {
>  			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
> -			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
> +			refer_to_commit(opts, &msgbuf, parent);
>  		}

...the way this is implemented means that we end up with a much more
verbose subject line in the case of reverts, which doesn't seem to be
intended (or at least not called out in the commit message).

I think a good solution to that would be to e.g. emit:

    # *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***

    Reverts commit <git reference>

    This revert of a merge reverts changes made to <git reference 2>.

Instead of what you have, which is:

    # *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***

    This reverts commit <git reference>, reversing
    changes made to <git reference 2>.

It's sharing a bit less code between the two, but I think the message is
suffering for it now.

I.e. the "Revert <reference>" change to "This reverts commit
<reference>" doesn't per-se seem intentional, but just a side-effect of
the optional "reference" revert's default "subject" line piggy-backing
on the non-"reference" body.

> +test_expect_success 'identification of reverted commit (default)' '
> +	test_commit to-ident &&
> +	test_when_finished "git reset --hard to-ident" &&
> +	git checkout --detach to-ident &&
> +	git revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git rev-parse HEAD^)." >expect &&

This pattern hides git exit codes & segfaults (I don't remember if I
mentioned that in a previous round, I think so...).

> +test_expect_success 'identification of reverted commit (--reference)' '
> +	git checkout --detach to-ident &&
> +	git revert --reference --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'identification of reverted commit (revert.reference)' '
> +	git checkout --detach to-ident &&
> +	git -c revert.reference=true revert --no-edit HEAD &&
> +	git cat-file commit HEAD >actual.raw &&
> +	grep "^This reverts " actual.raw >actual &&
> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
> +	test_cmp expect actual

Also (probably mentioned) I'd find this much easier to read/review if it
was using test_cmp, now you need to carefully parse the code to see what
the outputs are like exactly, but if we compared the full output...

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH v3] revert: optionally refer to commit in the "reference" format
  2022-06-01 15:14       ` Ævar Arnfjörð Bjarmason
@ 2022-06-01 21:52         ` Junio C Hamano
  0 siblings, 0 replies; 20+ messages in thread
From: Junio C Hamano @ 2022-06-01 21:52 UTC (permalink / raw)
  To: Ævar Arnfjörð Bjarmason
  Cc: git, Johannes Schindelin, Phillip Wood

Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:

> I think a good solution to that would be to e.g. emit:
>
>     # *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***
>
>     Reverts commit <git reference>
>
>     This revert of a merge reverts changes made to <git reference 2>.
>
> Instead of what you have, which is:
>
>     # *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***
>
>     This reverts commit <git reference>, reversing
>     changes made to <git reference 2>.
>
> It's sharing a bit less code between the two, but I think the message is
> suffering for it now.

We shouldn't be making it inconvenient for our primary intended
audience.

The real first line is designed to be usable without editing for
them.  Those who forgets to write the title and ends up with "This
reverts ..." as the title can still identify such a commit for the
purpose of "rebase -i" and "commit --fixup", and that is good enough
for them.

But your version will force the intended audience to remove the
"Reverts ..." line, that strikes the balance at the wrong place.

>> +test_expect_success 'identification of reverted commit (revert.reference)' '
>> +	git checkout --detach to-ident &&
>> +	git -c revert.reference=true revert --no-edit HEAD &&
>> +	git cat-file commit HEAD >actual.raw &&
>> +	grep "^This reverts " actual.raw >actual &&
>> +	echo "This reverts commit $(git show -s --pretty=reference HEAD^)." >expect &&
>> +	test_cmp expect actual
>
> Also (probably mentioned) I'd find this much easier to read/review if it
> was using test_cmp, now you need to carefully parse the code to see what
> the outputs are like exactly, but if we compared the full output...

We are using test_cmp.  'actual' has what we care about (i.e. what
does the line that begin with "This reverts " say?) and compares it
with what we expect to see in 'expect'.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-05-22  4:32 [PATCH] revert: optionally refer to commit in the "reference" format Junio C Hamano
                   ` (2 preceding siblings ...)
  2022-05-26 11:17 ` Phillip Wood
@ 2022-06-26  9:29 ` René Scharfe
  2022-06-27 15:38   ` Junio C Hamano
  3 siblings, 1 reply; 20+ messages in thread
From: René Scharfe @ 2022-06-26  9:29 UTC (permalink / raw)
  To: Junio C Hamano, git

Am 22.05.22 um 06:32 schrieb Junio C Hamano:
> ---
>  Documentation/config/revert.txt |  3 +++
>  Documentation/git-revert.txt    |  9 +++++++++
>  builtin/revert.c                |  2 ++
>  sequencer.c                     | 32 +++++++++++++++++++++++++++-----
>  sequencer.h                     |  1 +
>  t/t3501-revert-cherry-pick.sh   | 31 +++++++++++++++++++++++++++++++
>  6 files changed, 73 insertions(+), 5 deletions(-)
>  create mode 100644 Documentation/config/revert.txt
>
> diff --git a/Documentation/config/revert.txt b/Documentation/config/revert.txt
> new file mode 100644
> index 0000000000..797bfb6d62
> --- /dev/null
> +++ b/Documentation/config/revert.txt
> @@ -0,0 +1,3 @@
> +revert.reference::
> +	Setting this variable to true makes `git revert` to behave
> +	as if the `--reference` option is given.

Shouldn't this be "were" instead of "is"?  Not fully sure.  Anyway:

--- >8 ---
Subject: [PATCH] revert: config documentation fixes

43966ab315 (revert: optionally refer to commit in the "reference"
format, 2022-05-26) added the documentation file config/revert.txt.
Actually include it in config.txt.

Make is used with a bare infinitive after the object; remove the "to".

Signed-off-by: René Scharfe <l.s.r@web.de>
---
 Documentation/config.txt        | 2 ++
 Documentation/config/revert.txt | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index e284b042f2..e376d547ce 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -495,6 +495,8 @@ include::config/repack.txt[]

 include::config/rerere.txt[]

+include::config/revert.txt[]
+
 include::config/safe.txt[]

 include::config/sendemail.txt[]
diff --git a/Documentation/config/revert.txt b/Documentation/config/revert.txt
index 797bfb6d62..802d6faca2 100644
--- a/Documentation/config/revert.txt
+++ b/Documentation/config/revert.txt
@@ -1,3 +1,3 @@
 revert.reference::
-	Setting this variable to true makes `git revert` to behave
+	Setting this variable to true makes `git revert` behave
 	as if the `--reference` option is given.
--
2.36.1

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH] revert: optionally refer to commit in the "reference" format
  2022-06-26  9:29 ` René Scharfe
@ 2022-06-27 15:38   ` Junio C Hamano
  0 siblings, 0 replies; 20+ messages in thread
From: Junio C Hamano @ 2022-06-27 15:38 UTC (permalink / raw)
  To: René Scharfe; +Cc: git

René Scharfe <l.s.r@web.de> writes:

> Actually include it in config.txt.
>
> Make is used with a bare infinitive after the object; remove the "to".

Thanks.

^ permalink raw reply	[flat|nested] 20+ messages in thread

end of thread, other threads:[~2022-06-27 15:40 UTC | newest]

Thread overview: 20+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-05-22  4:32 [PATCH] revert: optionally refer to commit in the "reference" format Junio C Hamano
2022-05-23 13:25 ` Johannes Schindelin
2022-05-23 22:48   ` Junio C Hamano
2022-05-27  6:01     ` [PATCH v3] " Junio C Hamano
2022-05-30 16:40       ` Johannes Schindelin
2022-05-31 14:00       ` Phillip Wood
2022-06-01  4:45         ` Junio C Hamano
2022-06-01 15:03           ` Phillip Wood
2022-06-01 15:14       ` Ævar Arnfjörð Bjarmason
2022-06-01 21:52         ` Junio C Hamano
2022-05-30 16:50     ` Side effects in Git's test suite, was Re: [PATCH] " Johannes Schindelin
2022-05-31  8:03       ` Ævar Arnfjörð Bjarmason
2022-05-23 13:45 ` Ævar Arnfjörð Bjarmason
2022-05-23 22:37   ` Junio C Hamano
2022-05-24  8:12     ` Ævar Arnfjörð Bjarmason
2022-05-24 19:11       ` Junio C Hamano
2022-05-26 11:17 ` Phillip Wood
2022-05-26 17:29   ` Junio C Hamano
2022-06-26  9:29 ` René Scharfe
2022-06-27 15:38   ` Junio C Hamano

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