sequencer: run post-commit hook

Prior to commit 356ee4659b ("sequencer: try to commit without forking
'git commit'", 2017-11-24) the sequencer would always run the
post-commit hook after each pick or revert as it forked `git commit` to
create the commit. The conversion to committing without forking `git
commit` omitted to call the post-commit hook after creating the commit.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sequencer.c

@@ -1401,6 +1401,7 @@ static int try_to_commit(struct repository *r,
 		goto out;
 	}
 
+	run_commit_hook(0, r->index_file, "post-commit", NULL);
 	if (flags & AMEND_MSG)
 		commit_post_rewrite(r, current_head, oid);