[PATCH 0/2] [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP

[PATCH 0/2] [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP

[ZheNing Hu via GitGitGadget]

This patch fixes the bug when git cherry-pick is used with environment
variable GIT_CHERRY_PICK_HELP, and makes git chery-pick advice message
better.

v2:
https://lore.kernel.org/git/pull.1001.v2.git.1627135281887.gitgitgadget@gmail.com/

v2-->v3:

 1. Add hidden option --rebase-preserve-merges-mode to git cherry-pick.
 2. Split print_advice() into itself and
    check_need_delete_cherry_pick_head().
 3. Only allow git cherry-pick skip check_need_delete_cherry_pick_head().
 4. Use better git cherry-pick advice message.

ZheNing Hu (2):
  [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP
  [GSOC] cherry-pick: use better advice message

 builtin/revert.c                |  2 ++
 git-rebase--preserve-merges.sh  |  2 +-
 sequencer.c                     | 45 +++++++++++++++++++++++----------
 sequencer.h                     |  1 +
 t/t3507-cherry-pick-conflict.sh | 44 +++++++++++++++++++++-----------
 5 files changed, 64 insertions(+), 30 deletions(-)


base-commit: daab8a564f8bbac55f70f8bf86c070e001a9b006
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1007%2Fadlternative%2Fcherry-pick-help-fix-2-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1007/adlternative/cherry-pick-help-fix-2-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1007
-- 
gitgitgadget

[PATCH 1/2] [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP

[ZheNing Hu via GitGitGadget]

From: ZheNing Hu <adlternative@gmail.com>

GIT_CHERRY_PICK_HELP is an environment variable, as the
implementation detail of some porcelain in git to help realize
the rebasing steps. E.g. `git rebase -p` set GIT_CHERRY_PICK_HELP
value in git-rebase--preserve-merges.sh. But If we set the value
of GIT_CHERRY_PICK_HELP when using `git cherry-pick`, CHERRY_PICK_HEAD
will be deleted, then we will get an error when we try to use
`git cherry-pick --continue` or other cherr-pick command.

Introduce new "hidden" option --rebase-preserve-merges-mode for git
cherry-pick which indicates that git cherry-pick is currently called by
git-rebase--preserve-merges.sh. After `git rebase -p` completely
abolished, this option should be removed.

And then we split print_advice() into two part:
check_need_delete_cherry_pick_head() check if we set
GIT_CHERRY_PICK_HELP, if set, delete CHERRY_PICK_HEAD and return
GIT_CHERRY_PICK_HELP's value, if not set, return NULL; The parameters
of print_advice() have changed, which now accept a
`struct replay_opts *opt` and a `const char *help_msgs`. We can pass
the value of GIT_CHERRY_PICK_HELP into print_advice(), and output it.
In this way, the steps of printing advice and checking
GIT_CHERRY_PICK_HELP are decoupled.

Finally, avoid deleting CHERRY_PICK_HEAD when we are truly
cherry-picking, which can fix this breakage.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by Hariom Verma <hariom18599@gmail.com>:
Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Hepled-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
 builtin/revert.c                |  2 ++
 git-rebase--preserve-merges.sh  |  2 +-
 sequencer.c                     | 36 ++++++++++++++++++++-------------
 sequencer.h                     |  1 +
 t/t3507-cherry-pick-conflict.sh | 27 ++++++++++++++++---------
 5 files changed, 43 insertions(+), 25 deletions(-)

diff --git a/builtin/revert.c b/builtin/revert.c
index 237f2f18d4c..6165bb10143 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -127,6 +127,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 			OPT_BOOL(0, "allow-empty", &opts->allow_empty, N_("preserve initially empty commits")),
 			OPT_BOOL(0, "allow-empty-message", &opts->allow_empty_message, N_("allow commits with empty messages")),
 			OPT_BOOL(0, "keep-redundant-commits", &opts->keep_redundant_commits, N_("keep redundant, empty commits")),
+			OPT_BOOL_F(0, "rebase-preserve-merges-mode", &opts->rebase_preserve_merges_mode,
+				   N_("use for git-rebase--preserve-merges backend"), PARSE_OPT_HIDDEN),
 			OPT_END(),
 		};
 		options = parse_options_concat(options, cp_extra);
diff --git a/git-rebase--preserve-merges.sh b/git-rebase--preserve-merges.sh
index b9c71d2a71b..ca97d9b6539 100644
--- a/git-rebase--preserve-merges.sh
+++ b/git-rebase--preserve-merges.sh
@@ -444,7 +444,7 @@ pick_one_preserving_merges () {
 			output eval git cherry-pick $allow_rerere_autoupdate \
 				$allow_empty_message \
 				${gpg_sign_opt:+$(git rev-parse --sq-quote "$gpg_sign_opt")} \
-				"$strategy_args" "$@" ||
+				"$strategy_args" --rebase-preserve-merges-mode "$@" ||
 				die_with_patch $sha1 "$(eval_gettext "Could not pick \$sha1")"
 			;;
 		esac
diff --git a/sequencer.c b/sequencer.c
index 0bec01cf38e..ceaf73a34df 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -397,13 +397,11 @@ static void free_message(struct commit *commit, struct commit_message *msg)
 	unuse_commit_buffer(commit, msg->message);
 }
 
-static void print_advice(struct repository *r, int show_hint,
-			 struct replay_opts *opts)
+static char *check_need_delete_cherry_pick_head(struct repository *r)
 {
 	char *msg = getenv("GIT_CHERRY_PICK_HELP");
 
 	if (msg) {
-		fprintf(stderr, "%s\n", msg);
 		/*
 		 * A conflict has occurred but the porcelain
 		 * (typically rebase --interactive) wants to take care
@@ -411,18 +409,22 @@ static void print_advice(struct repository *r, int show_hint,
 		 */
 		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
 				NULL, 0);
-		return;
+		return msg;
 	}
+	return NULL;
+}
 
-	if (show_hint) {
-		if (opts->no_commit)
-			advise(_("after resolving the conflicts, mark the corrected paths\n"
-				 "with 'git add <paths>' or 'git rm <paths>'"));
-		else
-			advise(_("after resolving the conflicts, mark the corrected paths\n"
-				 "with 'git add <paths>' or 'git rm <paths>'\n"
-				 "and commit the result with 'git commit'"));
-	}
+static void print_advice(struct replay_opts *opts, const char *help_msgs)
+{
+	if (help_msgs)
+		advise("%s\n", help_msgs);
+	else if (opts->no_commit)
+		advise(_("after resolving the conflicts, mark the corrected paths\n"
+			 "with 'git add <paths>' or 'git rm <paths>'"));
+	else
+		advise(_("after resolving the conflicts, mark the corrected paths\n"
+			 "with 'git add <paths>' or 'git rm <paths>'\n"
+			 "and commit the result with 'git commit'"));
 }
 
 static int write_message(const void *buf, size_t len, const char *filename,
@@ -2261,11 +2263,17 @@ static int do_pick_commit(struct repository *r,
 		res = -1;
 
 	if (res) {
+		const char *help_msgs = NULL;
+
 		error(command == TODO_REVERT
 		      ? _("could not revert %s... %s")
 		      : _("could not apply %s... %s"),
 		      short_commit_name(commit), msg.subject);
-		print_advice(r, res == 1, opts);
+		if (((opts->action == REPLAY_PICK &&
+		      !opts->rebase_preserve_merges_mode) ||
+		      (help_msgs = check_need_delete_cherry_pick_head(r))) &&
+		      res == 1)
+			print_advice(opts, help_msgs);
 		repo_rerere(r, opts->allow_rerere_auto);
 		goto leave;
 	}
diff --git a/sequencer.h b/sequencer.h
index d57d8ea23d7..5a40b6d8bdc 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 rebase_preserve_merges_mode;
 
 	int mainline;
 
diff --git a/t/t3507-cherry-pick-conflict.sh b/t/t3507-cherry-pick-conflict.sh
index 014001b8f32..6f8035399d9 100755
--- a/t/t3507-cherry-pick-conflict.sh
+++ b/t/t3507-cherry-pick-conflict.sh
@@ -76,6 +76,23 @@ test_expect_success 'advice from failed cherry-pick --no-commit' "
 	test_cmp expected actual
 "
 
+test_expect_success 'advice from failed cherry-pick with GIT_CHERRY_PICK_HELP' "
+	pristine_detach initial &&
+	(
+		picked=\$(git rev-parse --short picked) &&
+		cat <<-EOF >expected &&
+		error: could not apply \$picked... picked
+		hint: after resolving the conflicts, mark the corrected paths
+		hint: with 'git add <paths>' or 'git rm <paths>'
+		hint: and commit the result with 'git commit'
+		EOF
+		GIT_CHERRY_PICK_HELP='and then do something else' &&
+		export GIT_CHERRY_PICK_HELP &&
+		test_must_fail git cherry-pick picked 2>actual &&
+		test_cmp expected actual
+	)
+"
+
 test_expect_success 'failed cherry-pick sets CHERRY_PICK_HEAD' '
 	pristine_detach initial &&
 	test_must_fail git cherry-pick picked &&
@@ -109,16 +126,6 @@ test_expect_success \
 	test_must_fail git rev-parse --verify CHERRY_PICK_HEAD
 '
 
-test_expect_success 'GIT_CHERRY_PICK_HELP suppresses CHERRY_PICK_HEAD' '
-	pristine_detach initial &&
-	(
-		GIT_CHERRY_PICK_HELP="and then do something else" &&
-		export GIT_CHERRY_PICK_HELP &&
-		test_must_fail git cherry-pick picked
-	) &&
-	test_must_fail git rev-parse --verify CHERRY_PICK_HEAD
-'
-
 test_expect_success 'git reset clears CHERRY_PICK_HEAD' '
 	pristine_detach initial &&
 
-- 
gitgitgadget

[PATCH 2/2] [GSOC] cherry-pick: use better advice message

[ZheNing Hu via GitGitGadget]

From: ZheNing Hu <adlternative@gmail.com>

In the past, git cherry-pick would print such advice when
there was a conflict:

hint: after resolving the conflicts, mark the corrected paths
hint: with 'git add <paths>' or 'git rm <paths>'
hint: and commit the result with 'git commit'

But in fact, when we want to cherry-pick multiple commits,
we should not use "git commit" after resolving conflicts, which
will make Git generate some errors. We should recommend users to
use `git cherry-pick --continue`, `git cherry-pick --abort`, just
like git rebase does.

This is the improved advice:

hint: Resolve all conflicts manually, mark them as resolved with
hint: "git add/rm <conflicted_files>", then run "git cherry-pick \
--continue".
hint: You can instead skip this commit: run "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by Hariom Verma <hariom18599@gmail.com>:
Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Hepled-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: ZheNing Hu <adlternative@gmail.com>
---
 sequencer.c                     | 19 ++++++++++++++-----
 t/t3507-cherry-pick-conflict.sh | 23 +++++++++++++++--------
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index ceaf73a34df..b9adeb7e5f5 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -39,6 +39,16 @@
 
 static const char sign_off_header[] = "Signed-off-by: ";
 static const char cherry_picked_prefix[] = "(cherry picked from commit ";
+static const char *no_commit_advice = N_("after resolving the conflicts, mark the corrected paths\n"
+				"with 'git add <paths>' or 'git rm <paths>'");
+static const char *commit_advice = N_("after resolving the conflicts, mark the corrected paths\n"
+			    "with 'git add <paths>' or 'git rm <paths>'\n"
+			    "and commit the result with 'git commit'");
+static const char *cherry_pick_advice = N_("Resolve all conflicts manually, mark them as resolved with\n"
+					"\"git add/rm <conflicted_files>\", then run \"git cherry-pick --continue\".\n"
+					"You can instead skip this commit: run \"git cherry-pick --skip\".\n"
+					"To abort and get back to the state before \"git cherry-pick\",\n"
+					"run \"git cherry-pick --abort\".");
 
 GIT_PATH_FUNC(git_path_commit_editmsg, "COMMIT_EDITMSG")
 
@@ -419,12 +429,9 @@ static void print_advice(struct replay_opts *opts, const char *help_msgs)
 	if (help_msgs)
 		advise("%s\n", help_msgs);
 	else if (opts->no_commit)
-		advise(_("after resolving the conflicts, mark the corrected paths\n"
-			 "with 'git add <paths>' or 'git rm <paths>'"));
+		advise("%s\n", _(no_commit_advice));
 	else
-		advise(_("after resolving the conflicts, mark the corrected paths\n"
-			 "with 'git add <paths>' or 'git rm <paths>'\n"
-			 "and commit the result with 'git commit'"));
+		advise("%s\n", _(commit_advice));
 }
 
 static int write_message(const void *buf, size_t len, const char *filename,
@@ -2269,6 +2276,8 @@ static int do_pick_commit(struct repository *r,
 		      ? _("could not revert %s... %s")
 		      : _("could not apply %s... %s"),
 		      short_commit_name(commit), msg.subject);
+		if (opts->action == REPLAY_PICK)
+			help_msgs = _(cherry_pick_advice);
 		if (((opts->action == REPLAY_PICK &&
 		      !opts->rebase_preserve_merges_mode) ||
 		      (help_msgs = check_need_delete_cherry_pick_head(r))) &&
diff --git a/t/t3507-cherry-pick-conflict.sh b/t/t3507-cherry-pick-conflict.sh
index 6f8035399d9..bf77bb0bd50 100755
--- a/t/t3507-cherry-pick-conflict.sh
+++ b/t/t3507-cherry-pick-conflict.sh
@@ -53,9 +53,11 @@ test_expect_success 'advice from failed cherry-pick' "
 	picked=\$(git rev-parse --short picked) &&
 	cat <<-EOF >expected &&
 	error: could not apply \$picked... picked
-	hint: after resolving the conflicts, mark the corrected paths
-	hint: with 'git add <paths>' or 'git rm <paths>'
-	hint: and commit the result with 'git commit'
+	hint: Resolve all conflicts manually, mark them as resolved with
+	hint: \"git add/rm <conflicted_files>\", then run \"git cherry-pick --continue\".
+	hint: You can instead skip this commit: run \"git cherry-pick --skip\".
+	hint: To abort and get back to the state before \"git cherry-pick\",
+	hint: run \"git cherry-pick --abort\".
 	EOF
 	test_must_fail git cherry-pick picked 2>actual &&
 
@@ -68,8 +70,11 @@ test_expect_success 'advice from failed cherry-pick --no-commit' "
 	picked=\$(git rev-parse --short picked) &&
 	cat <<-EOF >expected &&
 	error: could not apply \$picked... picked
-	hint: after resolving the conflicts, mark the corrected paths
-	hint: with 'git add <paths>' or 'git rm <paths>'
+	hint: Resolve all conflicts manually, mark them as resolved with
+	hint: \"git add/rm <conflicted_files>\", then run \"git cherry-pick --continue\".
+	hint: You can instead skip this commit: run \"git cherry-pick --skip\".
+	hint: To abort and get back to the state before \"git cherry-pick\",
+	hint: run \"git cherry-pick --abort\".
 	EOF
 	test_must_fail git cherry-pick --no-commit picked 2>actual &&
 
@@ -82,9 +87,11 @@ test_expect_success 'advice from failed cherry-pick with GIT_CHERRY_PICK_HELP' "
 		picked=\$(git rev-parse --short picked) &&
 		cat <<-EOF >expected &&
 		error: could not apply \$picked... picked
-		hint: after resolving the conflicts, mark the corrected paths
-		hint: with 'git add <paths>' or 'git rm <paths>'
-		hint: and commit the result with 'git commit'
+		hint: Resolve all conflicts manually, mark them as resolved with
+		hint: \"git add/rm <conflicted_files>\", then run \"git cherry-pick --continue\".
+		hint: You can instead skip this commit: run \"git cherry-pick --skip\".
+		hint: To abort and get back to the state before \"git cherry-pick\",
+		hint: run \"git cherry-pick --abort\".
 		EOF
 		GIT_CHERRY_PICK_HELP='and then do something else' &&
 		export GIT_CHERRY_PICK_HELP &&
-- 
gitgitgadget

Re: [PATCH 1/2] [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP

[Junio C Hamano]

"ZheNing Hu via GitGitGadget" <gitgitgadget@gmail.com> writes:

> -static void print_advice(struct repository *r, int show_hint,
> -			 struct replay_opts *opts)
> +static char *check_need_delete_cherry_pick_head(struct repository *r)
>  {
>  	char *msg = getenv("GIT_CHERRY_PICK_HELP");
>  
>  	if (msg) {
> -		fprintf(stderr, "%s\n", msg);
>  		/*
>  		 * A conflict has occurred but the porcelain
>  		 * (typically rebase --interactive) wants to take care
> @@ -411,18 +409,22 @@ static void print_advice(struct repository *r, int show_hint,
>  		 */
>  		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
>  				NULL, 0);
> -		return;
> +		return msg;
>  	}
> +	return NULL;
> +}

The patch is a bit hard to read, but I do not think this improves
the root cause of the issue at all, which is that "do we need to
delete the pseudoref?" decision is tied to and based on the presense
of the custom message in the environment variable.

The original issue was that we declared (erroneously) that the
presence of a custom message _means_ the caller is not a human but a
sequencing machinery that wants to deal with what is done via the
CHERRY_PICK_HEAD pseudoref itself, and your original issue was that
when a human user has the custom message envirnoment (either on
purpose or by mistake), the logic _misidentifies_ the call as if it
is made from a sequencing machinery and we lose the CHERRY_PICK_HEAD
pseudoref.  The root cause is mistaking the correlation (sequencing
machinery uses the environment and it also does not want pseudoref)
as the causation (presense of the environment means we should remove
pseudoref).

Re: [PATCH 1/2] [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP

[ZheNing Hu]

Junio C Hamano <gitster@pobox.com> 于2021年7月30日周五 上午4:56写道：
>
> The patch is a bit hard to read, but I do not think this improves
> the root cause of the issue at all, which is that "do we need to
> delete the pseudoref?" decision is tied to and based on the presense
> of the custom message in the environment variable.
>

My original idea was to distinguish between cherry-pick calls by machines
(git-rebase--preserve-merges.sh) and cherry-pick calls by people through
an additional option "rebase-preserve-merges-mode".

> The original issue was that we declared (erroneously) that the
> presence of a custom message _means_ the caller is not a human but a
> sequencing machinery that wants to deal with what is done via the
> CHERRY_PICK_HEAD pseudoref itself, and your original issue was that
> when a human user has the custom message envirnoment (either on
> purpose or by mistake), the logic _misidentifies_ the call as if it
> is made from a sequencing machinery and we lose the CHERRY_PICK_HEAD
> pseudoref.  The root cause is mistaking the correlation (sequencing
> machinery uses the environment and it also does not want pseudoref)
> as the causation (presense of the environment means we should remove
> pseudoref).

Ok... Now I guess what you mean is to provide an option for git cherry-pick
to specifically delete "CHERRY_PICK_HEAD", and this options is "hidden",
it is not provided to users, it is only reserved for sequencing
machinery. In this
way, we separate print_advice() from deleting "CHERRY_PICK_HEAD".
Then in the future, GIT_CHERRY_PICK_HELP will be deleted.

Thanks,
--
ZheNing Hu

[PATCH 0/2] [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP

[ZheNing Hu via GitGitGadget]

This patch fixes the bug when git cherry-pick is used with environment
variable GIT_CHERRY_PICK_HELP, and makes git chery-pick advice message
better.

v3:
https://lore.kernel.org/git/pull.1007.git.1627561665.gitgitgadget@gmail.com/

v3-->v4:

 1. Add hidden option --delete-cherry-pick-head to git cherry-pick wihch
    used to delete CHERRY_PICK_HEAD when conflict occurs.
 2. add delete_cherry_pick_head flag to struct replay_opts and struct
    rebase_options.
 3. Split print_advice() into print advice and delete CHERRY_PICK_HEAD two
    part.
 4. Use better git cherry-pick advice message.

ZheNing Hu (2):
  [GSOC] cherry-pick: fix bug when used with GIT_CHERRY_PICK_HELP
  [GSOC] cherry-pick: use better advice message

 builtin/rebase.c                |  3 +++
 builtin/revert.c                |  2 ++
 git-rebase--preserve-merges.sh  |  2 +-
 sequencer.c                     | 37 +++++++++++++++++-------------
 sequencer.h                     |  1 +
 t/t3507-cherry-pick-conflict.sh | 40 ++++++++++++++++++++-------------
 6 files changed, 53 insertions(+), 32 deletions(-)


base-commit: daab8a564f8bbac55f70f8bf86c070e001a9b006
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1010%2Fadlternative%2Fcherry-pick-help-fix-3-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1010/adlternative/cherry-pick-help-fix-3-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1010
-- 
gitgitgadget