Re: [PATCH] git: Use merge-base instead of log for testing if a commit is present

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Mon, 2013-11-18 at 19:32 +0100, Martin Jansa wrote:
> On Mon, Nov 18, 2013 at 05:17:16PM +0000, Richard Purdie wrote:
> > The current use of git log to check if a given revision is present can be
> > a little fragile.
> > 
> > For example if revision X was on branch A, and then later added to branch
> > B, the update checks would not notice this since they just check for X
> > being in the repository.
> > 
> > We also had some autobuilder corruption where an older packed-refs file
> > was copied over a new repository containing newer pack files. There
> > was no update to the refs file since the revision was present but
> > not accessible in any branch.
> > 
> > The correct fix is to check that the required revisions are present
> > on the specific branches. This patch does this using merge-base.
> 
> I guess that merge-base is probably faster or easier to use, but did you
> consider using git branch --contains?
> 
> e.g. checking if selected branch is in
> git branch --contains ud.revisions[name]
> 
> I'm asking only because I'm using "git branch --contains" in some
> scripts and maybe there is good reason I should rewrite them to use git
> merge-base instead.

git branch --contains gives you a branch list back which you'd have to
then parse to see if branch X was listed. git merge-base is faster and
we can directly ask what we need with an exit code. There is no more
deeply technical reason than that, was just neater.

Cheers,

Richard