Ævar Arnfjörð Bjarmason [off-list ref] writes:
On Sun, Feb 14 2021, René Scharfe wrote:
quoted
Add a format placeholder for describe output. Implement it by actually
calling git describe, which is simple and guarantees correctness. It's
intended to be used with $Format:...$ in files with the attribute
export-subst and git archive.
Does it really guarantee correctness though? In "builtin/describe.c" we
first walk over the refs and use that to format all N items we're asked
about.
Under "git log" this is presumably in a race where refs added/deleted
during the run of "git log" will change the describe output to be
inconsistent with earlier lines.
Yes, but it is not a news that the describe for a given commit will
not stay the constant while you add more objects to the repository
or you change the tags, whether the "describe" is driven internally
by "git log" or by the end-user, so I am not sure how that becomes
an issue. If the output is inconsistent in a quiescent repository,
that would be a problem, though.
Puzzled.
Thanks.
On Tue, Feb 16 2021, Junio C Hamano wrote:
Ævar Arnfjörð Bjarmason [off-list ref] writes:
quoted
On Sun, Feb 14 2021, René Scharfe wrote:
quoted
Add a format placeholder for describe output. Implement it by actually
calling git describe, which is simple and guarantees correctness. It's
intended to be used with $Format:...$ in files with the attribute
export-subst and git archive.
Does it really guarantee correctness though? In "builtin/describe.c" we
first walk over the refs and use that to format all N items we're asked
about.
Under "git log" this is presumably in a race where refs added/deleted
during the run of "git log" will change the describe output to be
inconsistent with earlier lines.
Yes, but it is not a news that the describe for a given commit will
not stay the constant while you add more objects to the repository
or you change the tags, whether the "describe" is driven internally
by "git log" or by the end-user, so I am not sure how that becomes
an issue. If the output is inconsistent in a quiescent repository,
that would be a problem, though.
Puzzled.
Usually something shelling out has going for it is that even if it's
slow it's at least known to be bug-free, after all we use the command
like that already.
I just wanted to point out this edge case, for "git describe <commits>"
we do the ref list once at the beginning so our N list will be
consistent within itself.
Whereas one might expect "git log" to also format such a list, but due
to the internal implementation the semantics are different.
Am 17.02.21 um 01:47 schrieb Ævar Arnfjörð Bjarmason:
Usually something shelling out has going for it is that even if it's
slow it's at least known to be bug-free, after all we use the command
like that already.
I just wanted to point out this edge case, for "git describe <commits>"
we do the ref list once at the beginning so our N list will be
consistent within itself.
Whereas one might expect "git log" to also format such a list, but due
to the internal implementation the semantics are different.
It shouldn't matter for the intended use case (git archive containing a
spec file with a single "$Format:%(describe)$") and I cannot imagine how
consistency in the face of tag changes would be useful (what application
would be OK with consistently outdated output, but break with partly
outdated descriptions). But it makes sense to mention it in the docs.
-- >8 --
Subject: [PATCH] pretty: document multiple %(describe) being inconsistent
Each %(describe) placeholder is expanded using a separate git describe
call. Their outputs depend on the tags present at the time, so there's
no consistency guarantee. Document that fact.
Reported-by: Ævar Arnfjörð Bjarmason <redacted>
Signed-off-by: René Scharfe <redacted>
---
Documentation/pretty-formats.txt | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 231010e6ef..45133066e4 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -212,7 +212,9 @@ The placeholders are:
linkgit:git-describe[1]; empty string for
undescribable commits. The `describe` string
may be followed by a colon and zero or more
- comma-separated options.
+ comma-separated options. Descriptions can be
+ inconsistent when tags are added or removed at
+ the same time.
+
** 'match=<pattern>': Only consider tags matching the given
`glob(7)` pattern, excluding the "refs/tags/" prefix.
--2.30.1