Re: How to embed a hash, tag or branch name?

["Dirk Süsserott" <newsletter@dirk.my1.cc>]

Am 01.08.2009 15:13 schrieb Jakub Narebski:
> On Sat, 1 August 2009, Dirk Süsserott wrote:
>> Am 31.07.2009 11:52 schrieb Mikko Rapeli:
>>> On Fri, Jul 31, 2009 at 02:27:50AM -0700, Jakub Narebski wrote:
> 
>>>> You can embed SHA-1 of a _file contents_ (blob) using '$Id: $' keyword
>>>> with `ident` attribute - see gitattributes manpage.
>>> Great, thanks!
>>>
>>>> The correct solution of embedding version number is to do it at 
>>>> _build time_, using e.g. script similar to GIT-VERSION-GEN used by
>>>> Git itself and by Linux kernel.  It helps if you tag your releases.
>> Hi Mikko,
>>
>> I don't know whether you want to use the "ident" command on your final
>> binary. With Git, that's pointless, as all source files will have the
>> same $Id$. So it's perfectly sufficient to have only ONE file enriched
>> with Git's SHA1.
> 
> You are wrong.  In Git $Id$ / $Id: $ expands to SHA-1 id of _blob_ 
> (i.e. of file *contents*), not SHA-1 id of a commit.  This way when
> switching branches or rewinding branch using git-reset we don't have
> to pay huge performance penalty because of `ident`, as we would have
> because every file would have to be changed if $Id$ was about commit
> id (or if there was $Revision$ or $Author$ implemented).

Ok, sorry about that. Actually I haven't read the concerning docs
*that* well when I figured out that keyword expansion with Git
is not exactly a good idea.

> 
>> Suggestion: During build time, compile (and link in) a file (e.g.
>> version.c) with "-DVERSION=\"$(git describe)\"". My version.c looks like
>> this:
> 
> GIT-VERSION-GEN and various tricks in Makefile do just that, not only
> for compiled parts, but also for scripts.
> 

Right, but my explanation shows the overall intention of that.
So, Mikko, have a look at GIT-VERSION-GEN and my suggestion and
use some kind of summary of them.