Re: [setup] Makefile.am patches

[Eric Blake <eblake at redhat dot com>]

On 02/18/2015 08:44 AM, Corinna Vinschen wrote:

>>
>> I inspected your code and played around with git-tag and git-describe
>> so it's ok.
> 
> While tagging for the next release, I noticed this:
> 
>   $ git describe
>   release_2.869-14-g10cac83
> 
>   $ git describe --match release_\* --abbrev=6 HEAD
>   release_2.869-14-g10cac8
> 
> See the missing 3?  Shouldn't that be --abbrev=7 in the Makefile?

--abbrev defaults to 7 unless specified; it can be as short as 4.  Git
guarantees that it will output something unambiguous at the time you do
the describe (so even if you request --abbrev=4, it may output 5 or 6
characters if 4 was ambiguous).  The probability of a collision is
higher at 4 than at 7 (when using --abbrev=4, I often see longer
entries; with --abbrev=7, I've occasionally seen an 8-character entry,
but it is much rarer).  The problem here is that something that is NOT
ambiguous right now might BECOME ambiguous in the future (that is, 4
characters may describe a commit now, but then collide with a future
commit and become ambiguous), so I agree that relying on the default of
7 (or omitting --abbrev from the Makefile altogether) is a safer bet to
avoid future collisions.

> 
> Next problem is this.  I just generated the annotation tag
> "release_2.870".  Now what?  Do I have to push?  Or how do I get this
> into the repo on sware?  git status tells me
> 
>   On branch master
>   Your branch is up-to-date with 'origin/master'.
>   nothing to commit, working directory clean

git push --tag release_2.870

> 
> Git is puzzeling...

Yeah, it's a hefty learning curve.  But once you get past that point,
you wonder how you ever survived on CVS.


-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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