Re: [PATCH v4] Allow update hooks to update refs on their own.

["Shawn O. Pearce" <spearce@spearce.org>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:
> On Sun, 2 Dec 2007, Shawn O. Pearce wrote:
> 
> > Steven Grimm <koreth@midwinter.com> wrote:
> > > This is useful in cases where a hook needs to modify an incoming commit
> > > in some way, e.g., fixing whitespace errors, adding an annotation to
> > > the commit message, noting the location of output from a profiling tool,
> > > or committing to an svn repository using git-svn.
> > ...
> > > +/* Update hook exit code: hook has updated ref on its own */
> > > +#define EXIT_CODE_REF_UPDATED 100
> > 
> > Hmm.  I would actually rather move the ref locking to before we run
> > the update hook, so the ref is locked *while* the hook executes.
> 
> Would that not mean that you cannot use update-ref to update the ref, 
> since that wants to use the same lock?

You failed to quote the part of my email where I talked about how
we set an evironment variable to pass a hint to lockfile.c running
within the git-update-ref subprocess to instruct it to perform a
different style of locking, one that would work as a "recursive"
lock.

Such a recursive lock could be useful for a whole lot more than just
the update hook.  But it would at least allow the update hook to
use git-update-ref to safely change the ref, without receive-pack
losing its own lock on the ref.

-- 
Shawn.