Re: [PATCH 1/2] pretty: add %(describe)

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.