Fwd: Discovering the new parents in commit hooks

[scott douglass <scott0douglass@gmail.com>]

Hi,

I’d like to be able to discover the new parents-to-be SHA-1s during
the hooks that run before a commit*.  Essentially I’d like be able to
distinguish the ‘git commit’ case from ‘git commit —amend’. Is there
already a way to do this that I have overlooked? (I’ve read ‘man
githooks’ and searched the wiki and various other places.)

If not, I would propose that perhaps the hooks could be passed a
GIT_PARENTS (or perhaps GIT_NEW_PARENTS) environment variable which in
the ‘not amend’ case would contain the SHA-1 for HEAD and MERGE_HEAD
(if appropriate) and in the ‘—amend' case would contain HEAD^@ (all of
the parents of HEAD).

[*] Specifically, it seems a useful thing to be able to find out in
these hooks:  applypatch-msg, pre-applypatch, commit-msg,
prepare-commit-msg, commit-msg

Thanks.