sequencer: run post-commit hook

Prior to commit 356ee46 ("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>

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);
 

t/t3404-rebase-interactive.sh

@@ -1583,6 +1583,25 @@ test_expect_success 'valid author header when author contains single quote' '
 	test_cmp expected actual
 '
 
+test_expect_success 'post-commit hook is called' '
+	test_when_finished "rm -f .git/hooks/post-commit" &&
+	>actual &&
+	mkdir -p .git/hooks &&
+	write_script .git/hooks/post-commit <<-\EOS &&
+	git rev-parse HEAD >>actual
+	EOS
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 4 1 reword 2 fixup 3" git rebase -i A E &&
+		echo x>file3 &&
+		git add file3 &&
+		FAKE_COMMIT_MESSAGE=edited git rebase --continue
+	) &&
+	git rev-parse HEAD@{5} HEAD@{4} HEAD@{3} HEAD@{2} HEAD@{1} HEAD \
+		>expect &&
+	test_cmp expect actual
+'
+
 # This must be the last test in this file
 test_expect_success '$EDITOR and friends are unchanged' '
 	test_editor_unchanged