[Mesa-dev] [PATCH] automake: increase the MESA_GIT_SHA1 hash id length from 7 to 10 digits

[Eric Engestrom]

On Thursday, 2017-06-15 09:56:55 +0100, Emil Velikov wrote:
> Hi Brian,
> 
> On 15 June 2017 at 04:46, Brian Paul <brianp at vmware.com> wrote:
> > The SCons build has been using 10 digits of the git hash id for the
> > MESA_GIT_SHA1 string in git_sha1.h for about a year now.  I bumped it
> > up after running into a case where a 7-digit hash ID was ambiguous.
> >
> > This patch makes the same change for the autotools build.
> >
> > The command "git log | grep "^commit" | cut -b 8-14 | sort | uniq -d"
> > shows there are currently 17 cases where 7 digits of hash id are
> > ambiguous on master (probably quite a few more if we'd consider other
> > branches).
> >
> > Instead of using "git log -n 1 --oneline" use
> > "git rev-parse --short=10 HEAD" to get the HEAD hash id.
> 
> The current command produces 11 digit SHA

That would depend on your git version (it used to be 7 until early 2.x
and is 10 on my 2.13.1), and your core.abbrev config :)

> and size will grow automatically as needed.

Ack, but only after the collision happens, I think the point is to be
big enough that the hash stored will be unique compared to (reasonably)
all the future versions. Being explicit about the min length does that.

Also, I prefer the use of `git rev-parse` rather than parsing the output
of `git log` :)

> Perhaps we should throw the logic in a small shell script and invoke
> it from the build system(s)?

Agreed.

> 
> -Emil