Re: why the 'g' prefix on the SHA1 in git-describe output?

From: Jim Meyering <jim@meyering.net>
Date: Nov 3, 2007, 16:10 UTC
Message-ID: <87ir4j71j0.fsf@rho.meyering.net>
In-Reply-To: <472C915E.8070205@op5.se>

Andreas Ericsson <ae@op5.se> wrote:

Show 19 quoted lines

> Lars Hjemli wrote:
>> On Nov 3, 2007 1:25 PM, Jim Meyering <jim@meyering.net> wrote:
>>> Can anyone tell me what motivated adding the 'g' prefix on the SHA1 in
>>> git-describe output?
>>
>> I'm not sure what _motivated_ the 'g', but currently git-rev-parse
>> understands the output from git-describe _if_ the 'g' is present.
>>
>
> It's been there since 908e5310b958619559d34b0b6da122f058faa47e, which
> has the commit-subject 'Add a "git-describe" command'.
>
> I think it'd be more trouble removing it now than it is to keep it,
> since a lot of script depend on it being there for parsing out
> versioning info in various autobuild- and release scripts.
>
> If you want to change it, I'd suggest adding a "--no-sha1" option
> that makes the entire "-g%s" part of the output go away, or
> perhaps adding a --format="%v-%d-%g" (for the default behaviour).

Thanks to both of you for the feedback. FYI, I didn't propose to change it in git.

I was wondering whether to restore the 'g' in snapshot version numbers for coreutils, autoconf, etc.:

  http://thread.gmane.org/gmane.comp.sysutils.autoconf.general/9784/focus=9811

Since coreutils version strings will end up having at least one more "." (currently they look like this: 6.9-375-3e3f8), that means transforming a version string into input for git-rev-parse will require the reverse xform. Once you're doing some transformation, an additional one to insert the required 'g' is no big deal, so I expect to continue omitting the 'g' from version strings: makes file names 1 byte shorter.