[PATCH 0/3] Iron output of describe --contains --all

[PATCH 0/3] Iron output of describe --contains --all

[Ramkumar Ramachandra]

Hi,

I actually sent these patches to the list last month, but nobody
seemed to be interested.  This is an unedited resend.

I looked into adding tests, but decided that it was a lost cause: the
output is too loosely defined for any scripts to rely on it strongly.
[1/3] already shows a race between branches and tags.  For another
example, consider two tags are pointing to same commit (D and R in
t6120-describe.sh).  Run the following on the two tags and see what
happens for yourself:

  $ git describe --contains
  $ git describe --all
  $ git describe --tags

Now think about various combinations of these options.  I'm not saying
that it's a Bad Thing (TM), but that nobody has bothered tightening
the output.

My main motivation for doing this series is my prompt: I don't want to
see

  artagnon|(tags/v1.8.3^0)~/src/git$

when

  artagnon|(v1.8.3)~/src/git$

is so much more pleasant and consistent.  Obviously, hacking around
this problem in the prompt script is the Wrong thing to do.

Thanks.

Ramkumar Ramachandra (3):
  name-rev: fix assumption about --name-only usage
  name-rev: strip trailing ^0 in when --name-only
  name-rev doc: rewrite --stdin paragraph

 Documentation/git-name-rev.txt       | 12 +++++++-----
 builtin/name-rev.c                   | 12 +++++++++++-
 t/t4202-log.sh                       |  8 ++++----
 t/t6007-rev-list-cherry-pick-file.sh | 32 ++++++++++++++++----------------
 4 files changed, 38 insertions(+), 26 deletions(-)

-- 
1.8.3.2.737.gcbc076a.dirty

[PATCH 1/3] name-rev: fix assumption about --name-only usage

[Ramkumar Ramachandra]

236157 (Teach git-describe how to run name-rev, 2007-05-21) introduced
`git name-rev --name-only`, with the intent of using it to implement
`git describe --contains`.  According to the message, users wanted to
use describe to figure out which tags contains a specific commit.
name-rev already did this, but didn't print out in the same format as
describe:

  $ git describe v1.8.3~1
  v1.8.3-rc3-8-g5e49f30

  $ git name-rev v1.8.3~1
  v1.8.3~1 tags/v1.8.3~1

There are two problems with using the output of name-rev in describe:
first, it prints out the given argument before describing it.  Second,
it prefixes "tags/" to the tag description.  To eliminate these two
problems, 236157 proposed that the --name-rev option would strip these
things when used with --tags, to match the describe output more closely:

  $ git name-rev --name-only --tags v1.8.3~1
  v1.8.3~1

236157 did not anticipate a problem with always combining --name-rev
with --tags, because it was primarily intended to be used from describe,
where it hard-coded these two arguments in the execv() of name-rev.

Later, 3f7701 (make 'git describe --all --contains' work, 2007-12-19)
noticed that describe didn't work with --contains and --all.  This is
because --contains implied a call to --name-rev (in with --tags was
hard-coded), but --all implied that any ref should be used to describe
the given argument (not just tags).  3f7701 took the band-aid approach,
and made --all disable --tags when calling name-rev.  As a result, while

  $ git describe --contains v1.8.3~1
  v1.8.3~1

would get name-rev to print output in the same format as describe,

  $ git describe --contains --all v1.8.3~1
  tags/v1.8.3~1

would not strip the leading "tags/".

The bug exists in git to this day.  Fix it by removing the assumption
that name-rev --name-only is only intended to be used with --tags.  Also
update some tests.

Users and scripts have learnt to live with 3f7701, and it will continue
to be a small quirk.  Even after this patch, notice

  $ git checkout -b foom v1.8.3
  $ git describe --contains @~1
  v1.8.3~1
  $ git describe --contains --all @~1
  foom~1

In other words, --contains implies --tags in name-rev, which gives
precedence to tags; --all cancels that effect thereby giving precedence
to branches in the case of a tie.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 Documentation/git-name-rev.txt       |  6 +++---
 builtin/name-rev.c                   |  3 +++
 t/t4202-log.sh                       |  8 ++++----
 t/t6007-rev-list-cherry-pick-file.sh | 32 ++++++++++++++++----------------
 4 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/Documentation/git-name-rev.txt b/Documentation/git-name-rev.txt
index 6b0f1ba..7cde4b3 100644
--- a/Documentation/git-name-rev.txt
+++ b/Documentation/git-name-rev.txt
@@ -37,9 +37,9 @@ OPTIONS
 
 --name-only::
 	Instead of printing both the SHA-1 and the name, print only
-	the name.  If given with --tags the usual tag prefix of
-	"tags/" is also omitted from the name, matching the output
-	of `git-describe` more closely.
+	the name.  The usual tag prefix of "tags/" is also omitted
+	from the name, matching the output of `git-describe` more
+	closely.
 
 --no-undefined::
 	Die with error code != 0 when a reference is undefined,
diff --git a/builtin/name-rev.c b/builtin/name-rev.c
index 87d4854..37207a9 100644
--- a/builtin/name-rev.c
+++ b/builtin/name-rev.c
@@ -138,6 +138,9 @@ static int name_ref(const char *path, const unsigned char *sha1, int flags, void
 			path = shorten_unambiguous_ref(path, 0);
 		else if (!prefixcmp(path, "refs/heads/"))
 			path = path + 11;
+		else if (data->name_only
+		    && !prefixcmp(path, "refs/tags/"))
+			path = path + 10;
 		else if (!prefixcmp(path, "refs/"))
 			path = path + 5;
 
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index cb03d28..9bec360 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -302,7 +302,7 @@ cat > expect <<\EOF
 | |
 | |     side-2
 | |
-| * commit tags/side-1
+| * commit side-1
 | | Author: A U Thor <author@example.com>
 | |
 | |     side-1
@@ -327,17 +327,17 @@ cat > expect <<\EOF
 |
 |       fourth
 |
-* commit tags/side-1~1
+* commit side-1~1
 | Author: A U Thor <author@example.com>
 |
 |     third
 |
-* commit tags/side-1~2
+* commit side-1~2
 | Author: A U Thor <author@example.com>
 |
 |     second
 |
-* commit tags/side-1~3
+* commit side-1~3
   Author: A U Thor <author@example.com>
 
       initial
diff --git a/t/t6007-rev-list-cherry-pick-file.sh b/t/t6007-rev-list-cherry-pick-file.sh
index 28d4f6b..5a8175e 100755
--- a/t/t6007-rev-list-cherry-pick-file.sh
+++ b/t/t6007-rev-list-cherry-pick-file.sh
@@ -49,8 +49,8 @@ test_expect_success setup '
 '
 
 cat >expect <<EOF
-<tags/B
->tags/C
+<B
+>C
 EOF
 
 test_expect_success '--left-right' '
@@ -70,7 +70,7 @@ test_expect_success '--cherry-pick foo comes up empty' '
 '
 
 cat >expect <<EOF
->tags/C
+>C
 EOF
 
 test_expect_success '--cherry-pick bar does not come up empty' '
@@ -88,8 +88,8 @@ test_expect_success 'bar does not come up empty' '
 '
 
 cat >expect <<EOF
-<tags/F
->tags/E
+<F
+>E
 EOF
 
 test_expect_success '--cherry-pick bar does not come up empty (II)' '
@@ -100,10 +100,10 @@ test_expect_success '--cherry-pick bar does not come up empty (II)' '
 '
 
 cat >expect <<EOF
-+tags/F
-=tags/D
-+tags/E
-=tags/C
++F
+=D
++E
+=C
 EOF
 
 test_expect_success '--cherry-mark' '
@@ -114,10 +114,10 @@ test_expect_success '--cherry-mark' '
 '
 
 cat >expect <<EOF
-<tags/F
-=tags/D
->tags/E
-=tags/C
+<F
+=D
+>E
+=C
 EOF
 
 test_expect_success '--cherry-mark --left-right' '
@@ -128,7 +128,7 @@ test_expect_success '--cherry-mark --left-right' '
 '
 
 cat >expect <<EOF
-tags/E
+E
 EOF
 
 test_expect_success '--cherry-pick --right-only' '
@@ -146,8 +146,8 @@ test_expect_success '--cherry-pick --left-only' '
 '
 
 cat >expect <<EOF
-+tags/E
-=tags/C
++E
+=C
 EOF
 
 test_expect_success '--cherry' '
-- 
1.8.3.2.737.gcbc076a.dirty

Re: [PATCH 1/3] name-rev: fix assumption about --name-only usage

[Junio C Hamano]

Ramkumar Ramachandra <artagnon@gmail.com> writes:

> 236157 (Teach git-describe how to run name-rev, 2007-05-21) introduced
> `git name-rev --name-only`, with the intent of using it to implement
> `git describe --contains`.  According to the message, users wanted to
> use describe to figure out which tags contains a specific commit.
> name-rev already did this, but didn't print out in the same format as
> describe:
>
>   $ git describe v1.8.3~1
>   v1.8.3-rc3-8-g5e49f30
>
> ...  As a result, while
>
>   $ git describe --contains v1.8.3~1
>   v1.8.3~1

The above two look consistent, yes.

>
> would get name-rev to print output in the same format as describe,
>
>   $ git describe --contains --all v1.8.3~1
>   tags/v1.8.3~1
>
> would not strip the leading "tags/".

If you _know_ v1.8.3 does not appear outside "tags/", this does look
inconsistent, but I do not think the code checks it.  Ahd if the
code does not, I am not sure not stripping "tags/" is necessarily a
bad thing, because "--all" allows names to come outside "tags/"
hierarchy.

Also how should this interact with v1.8.3-1-g98c5c4a that changed
the rule somewhat so that the common prefix is stripped when we know
the result is not ambiguous?

Re: [PATCH 1/3] name-rev: fix assumption about --name-only usage

[Ramkumar Ramachandra]

Junio C Hamano wrote:
>> would get name-rev to print output in the same format as describe,
>>
>>   $ git describe --contains --all v1.8.3~1
>>   tags/v1.8.3~1
>>
>> would not strip the leading "tags/".
>
> If you _know_ v1.8.3 does not appear outside "tags/", this does look
> inconsistent, but I do not think the code checks it.  Ahd if the
> code does not, I am not sure not stripping "tags/" is necessarily a
> bad thing, because "--all" allows names to come outside "tags/"
> hierarchy.

Yeah, you asked for it using --all.

> Also how should this interact with v1.8.3-1-g98c5c4a that changed
> the rule somewhat so that the common prefix is stripped when we know
> the result is not ambiguous?

Completely independent of everything else.  The condition is "if
name-only && prefix == refs/tags", strip that prefix.

[PATCH 2/3] name-rev: strip trailing ^0 in when --name-only

[Ramkumar Ramachandra]

236157 (Teach git-describe how to run name-rev, 2007-05-21) introduced
`git name-rev --name-only`, with the intent of using it to implement
`git describe --contains`.  According to the message, one of the primary
objectives of --name-only was to make the output of name-rev match that
of describe.

  $ git describe --contains --all master
  master

  $ git describe --contains --all master~1
  master~1

  $ git describe --contains --all v1.8.3~1
  v1.8.3~1

  $ git describe --contains --all v1.8.3
  v1.8.3^0

The last invocation unnecessarily prints a trailing "^0" (--stdin does
not suffer from this defect).  Fix this.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 builtin/name-rev.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/builtin/name-rev.c b/builtin/name-rev.c
index 37207a9..8ba5d72 100644
--- a/builtin/name-rev.c
+++ b/builtin/name-rev.c
@@ -186,7 +186,14 @@ static void show_name(const struct object *obj,
 	if (!name_only)
 		printf("%s ", caller_name ? caller_name : sha1_to_hex(sha1));
 	name = get_rev_name(obj);
-	if (name)
+
+	if (name && name_only) {
+		/* strip possible trailing ^0 from name */
+		int len = strlen(name);
+		if (len > 2 && !strcmp(name + len - 2, "^0"))
+			len -= 2;
+		printf("%.*s\n", len, name);
+	} else if (name)
 		printf("%s\n", name);
 	else if (allow_undefined)
 		printf("undefined\n");
-- 
1.8.3.2.737.gcbc076a.dirty

Re: [PATCH 2/3] name-rev: strip trailing ^0 in when --name-only

[Junio C Hamano]

Ramkumar Ramachandra <artagnon@gmail.com> writes:

> 236157 (Teach git-describe how to run name-rev, 2007-05-21) introduced
> `git name-rev --name-only`, with the intent of using it to implement
> `git describe --contains`.  According to the message, one of the primary
> objectives of --name-only was to make the output of name-rev match that
> of describe.
>
>   $ git describe --contains --all master
>   master
>
>   $ git describe --contains --all master~1
>   master~1
>
>   $ git describe --contains --all v1.8.3~1
>   v1.8.3~1
>
>   $ git describe --contains --all v1.8.3
>   v1.8.3^0

WRT "describe --contains", I do agree that both of these

    $ git describe $(git rev-parse v1.8.3^0)
    $ git describe --contains $(git rev-parse v1.8.3^0)
        
should just say "v1.8.3" without ~0/^0/~0~0~0 etc. and the last
example you showed will be improved by dropping ^0 at the end.

However.

I was a bit bothered by the description talking _only_ about
describe, but the actual change is to modify what name-rev gives its
direct users as well.  And that made me realize that the patch
itself has an undesirable side effect.

"describe" is _only_ about commit history graph, so in its context
v1.8.3 means the same thing as v1.8.3^0 (we never want to get a tag;
we always want a commit).  But I do not think "name-rev" is limited
to commits, in the sense that you would see this:

    $ git rev-parse v1.8.3 v1.8.3^0 | git name-rev --stdin
    8af06057d0c31a24e8737ae846ac2e116e8bafb9
    edca4152560522a431a51fc0a06147fc680b5b18 (tags/v1.8.3^0)

The second object is _not_ v1.8.3 but is v1.8.3^0 in the context of
name-rev, whose purpose is to give you a string you can feed
"rev-parse" and get the object name back.  "rev-parse v1.8.3" will
not give you the commit object name, so you need to keep "^0".

Re: [PATCH 2/3] name-rev: strip trailing ^0 in when --name-only

[Junio C Hamano]

Junio C Hamano <gitster@pobox.com> writes:

> WRT "describe --contains", I do agree that both of these
>
>     $ git describe $(git rev-parse v1.8.3^0)
>     $ git describe --contains $(git rev-parse v1.8.3^0)
>         
> should just say "v1.8.3" without ~0/^0/~0~0~0 etc. and the last
> example you showed will be improved by dropping ^0 at the end.
>
> However.
>
> I was a bit bothered by the description talking _only_ about
> describe, but the actual change is to modify what name-rev gives its
> direct users as well.  And that made me realize that the patch
> itself has an undesirable side effect.
>
> "describe" is _only_ about commit history graph, so in its context
> v1.8.3 means the same thing as v1.8.3^0 (we never want to get a tag;
> we always want a commit).  But I do not think "name-rev" is limited
> to commits, in the sense that you would see this:
>
>     $ git rev-parse v1.8.3 v1.8.3^0 | git name-rev --stdin
>     8af06057d0c31a24e8737ae846ac2e116e8bafb9
>     edca4152560522a431a51fc0a06147fc680b5b18 (tags/v1.8.3^0)
>
> The second object is _not_ v1.8.3 but is v1.8.3^0 in the context of
> name-rev, whose purpose is to give you a string you can feed
> "rev-parse" and get the object name back.  "rev-parse v1.8.3" will
> not give you the commit object name, so you need to keep "^0".

Well, the code in "name-rev" other than --stdin mode is already
broken (and the documentation half-describes this breakage) in that
it describes the peeled commit and rejects anything other than
commit objects.  The reason I say "half-describes" is that it only
says that the command takes "commit-ish" and leaves it unclear if it
comes up with a name for the tag itself that happens to be
commit-ish, or it does so for the commit that is referred by the
tag.

I'll send out a WIP to fix that, and also help the topic to strip
unnecessary "^0" suffix when name-rev is run as an implementation
detail of "describe" shortly.

Re: [PATCH 2/3] name-rev: strip trailing ^0 in when --name-only

[Ramkumar Ramachandra]

Junio C Hamano wrote:
> But I do not think "name-rev" is limited
> to commits, in the sense that you would see this:
>
>     $ git rev-parse v1.8.3 v1.8.3^0 | git name-rev --stdin
>     8af06057d0c31a24e8737ae846ac2e116e8bafb9
>     edca4152560522a431a51fc0a06147fc680b5b18 (tags/v1.8.3^0)
>
> The second object is _not_ v1.8.3 but is v1.8.3^0 in the context of
> name-rev, whose purpose is to give you a string you can feed
> "rev-parse" and get the object name back.  "rev-parse v1.8.3" will
> not give you the commit object name, so you need to keep "^0".

Quite frankly, I thought the unstripped ^0 in one codepath was an
unintended quirk.  What exactly do you want name-rev to give you?

  $ git tag foo @^
  $ git name-rev foo
  foo tags/foo

So you can distinguish between annotated tags, unannotated tags, and
head-refs.  Can you get it to tell you anything reliably though?

  $ git tag bar @
  $ git tag -a baz @
  $ git name-rev @
  $ git name-rev bar
  $ git name-rev baz

ref, annotated, or unannotated tag?  I do not think name-rev is
fundamentally different from describe: it is also only dependent on
the commit history graph.  Whether I specify a revision using @, HEAD,
baz, or bar, I should get the same answer (it's just a recursive
peeler).  I'm not sure what you gain by knowing the object type of the
output.  If you wanted to feed something into rev-parse and get out a
commit, you'd send in $REV^0 without bothering about what it is, no?

[PATCH 3/3] name-rev doc: rewrite --stdin paragraph

[Ramkumar Ramachandra]

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 Documentation/git-name-rev.txt | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Documentation/git-name-rev.txt b/Documentation/git-name-rev.txt
index 7cde4b3..94bded8 100644
--- a/Documentation/git-name-rev.txt
+++ b/Documentation/git-name-rev.txt
@@ -32,8 +32,10 @@ OPTIONS
 	List all commits reachable from all refs
 
 --stdin::
-	Read from stdin, append "(<rev_name>)" to all sha1's of nameable
-	commits, and pass to stdout
+	Transform stdin by substituting all the 40-character SHA-1
+	hexes (say $hex) with "$hex ($rev_name)".  When used with
+	--name-only, substitute with "$rev_name", omitting $hex
+	altogether.  Intended for the scripter's use.
 
 --name-only::
 	Instead of printing both the SHA-1 and the name, print only
-- 
1.8.3.2.737.gcbc076a.dirty

Re: [PATCH 3/3] name-rev doc: rewrite --stdin paragraph

[Junio C Hamano]

Ramkumar Ramachandra <artagnon@gmail.com> writes:

> Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
> ---
>  Documentation/git-name-rev.txt | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/git-name-rev.txt b/Documentation/git-name-rev.txt
> index 7cde4b3..94bded8 100644
> --- a/Documentation/git-name-rev.txt
> +++ b/Documentation/git-name-rev.txt
> @@ -32,8 +32,10 @@ OPTIONS
>  	List all commits reachable from all refs
>  
>  --stdin::
> -	Read from stdin, append "(<rev_name>)" to all sha1's of nameable
> -	commits, and pass to stdout
> +	Transform stdin by substituting all the 40-character SHA-1
> +	hexes (say $hex) with "$hex ($rev_name)".  When used with
> +	--name-only, substitute with "$rev_name", omitting $hex
> +	altogether.  Intended for the scripter's use.
>  
>  --name-only::
>  	Instead of printing both the SHA-1 and the name, print only

Looks obviously correct and more helpful description.

Thanks.