On Wed, Apr 25, 2018 at 11:18:26AM -0400, Marc Branchaud wrote:
> > The best approach to do so is to have those people do the "touch"
> > thing in their own post-checkout hook. People who use Git as the
> > source control system won't have to pay runtime cost of doing the
> > touch thing, and we do not have to maintain such a hook script.
> > Only those who use the "feature" would.
>
> The post-checkout hook approach is not exactly straightforward.
>
> Naively, it's simply
>
> for F in `git diff --name-only $1 $2`; do touch "$F"; done
Even this naive attempt gets it wrong: successive files have increasing
times. You need to capture the time at the start, and use it as the time
for the files.
touch /tmp/ref && \
for F in `git diff --name-only $1 $2`; do touch -r /tmp/ref "$F"; done && \
rm /tmp/ref
(or pass a fixed time into touch).
> But consider:
>
> * Symlinks can cause the wrong file to be touched. (Granted, Michał's
> proposed patch also doesn't deal with symlinks.)
Yes, it blindly touches the file, and rather than trying to do
utimensat's AT_SYMLINK_NOFOLLOW flag.
> Let's assume that a
> hook can be crafted will all possible sophistication. There are still
> some fundamental problems:
>
> * In a "file checkout" ("git checkout -- path/to/file"), $1 and $2 are
> identical so the above loop does nothing. Offhand I'm not even sure how
> a hook might get the right files in this case.
Yes, this would need to be a new hook that knows more than post-checkout
presently does.
post-checkout right now runs AFTER the worktree has been updated, and
only gets the refs of old/new HEAD and if the branch was changed.
It does NOT know which files were actually modified, and since it
If a hook is added for that, then this behavior can be implemented in
the hook. Alternatively adding a pre-checkout hook to absorb some state
of the unmodified worktree (this could be a bit expensive).
> * The hook has to be set up in every repo and submodule (at least until
> something like Ævar's experiments come to fruition).
>
> * A fresh clone can't run the hook. This is especially important when
> dealing with submodules. (In one case where we were bit by this, make
> though that half of a fresh submodule clone's files were stale, and
> decided to re-autoconf the entire thing.)
The fresh clone case really matters for my usage, where new clones are
firing in CI/CD processes.
> I just don't think the hook approach can completely solve the problem.
>
> I appreciate Ævar's concern that there are more than just two mtime
> requests floating around. But I think git's users are best served by a
> built-in approach, with a config setting to control the desired mtime
> handling (defaulting to the current behaviour). People who want a
> different mtime solution will at least have a clear place in the code to
> propose a patch.
+1 as long as we can set the behavior during the clone.
--
Robin Hugh Johnson
Gentoo Linux: Dev, Infra Lead, Foundation Treasurer
E-Mail : robbat2@xxxxxxxxxx
GnuPG FP : 11ACBA4F 4778E3F6 E4EDF38E B27B944E 34884E85
GnuPG FP : 7D0B3CEB E9B85B1F 825BCECF EE05E6F6 A48F6136
