From c14c3959edd605db06c99fe868177548e6008ec0 Mon Sep 17 00:00:00 2001
From: Tyrie Vella <tyrielv@gmail.com>
Date: Wed, 21 Oct 2026 11:01:45 -0700
Subject: [PATCH] hook: reset path before early hook lookup

find_hook() keeps the resolved path in a static strbuf. If the
repository has no gitdir yet, it calls hook_path_early(). That function
appends the hooks directory and the hook name to the buffer, but it does
not reset the buffer first. In v2.53.0.vfs.0.0, find_hook() called
strbuf_reset() before either branch. The rebase onto v2.54.0, which
includes upstream b51e238ddf8 (hook: allow out-of-repo 'git hook'
invocations), rewrote find_hook() and dropped that reset.

Because of this, a process that finds the pre-command hook before the
gitdir is set up cannot find post-command later in the same process. The
second lookup appends to the first path, so access() fails and the hook
is skipped. This affects dashed external commands, built-ins that do
not set up the repository (for example 'git version'), and the case
where a dashed external is not found and Git falls back to an alias.

VFS for Git takes a lock in pre-command and releases it in post-command.
If an external disappears between pre-command and dispatch, Git falls
back to the alias and starts a child Git process. The parent never runs
post-command, so the child waits for the parent's lock and the parent
waits for the child.

Reset the buffer before either branch. Add tests that check the
pre-command and post-command order for a dashed external command, for
'git version', and for a dashed external that disappears before the
alias fallback.

Assisted-by: Claude Opus 5.5
Signed-off-by: Tyrie Vella <tyrielv@gmail.com>
---
 hook.c                       |  1 +
 t/t0401-post-command-hook.sh | 61 ++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/hook.c b/hook.c
index 4b1b21839d265c..47e5b19b9783e3 100644
--- a/hook.c
+++ b/hook.c
@@ -81,6 +81,7 @@ const char *find_hook(struct repository *r, const char *name)
 
 	int found_hook;
 
+	strbuf_reset(&path);
 	if (!r || !r->gitdir) {
 		if (!hook_path_early(name, &path))
 			return NULL;
diff --git a/t/t0401-post-command-hook.sh b/t/t0401-post-command-hook.sh
index 41cbbbc2c6ba10..8c33835f4d434b 100755
--- a/t/t0401-post-command-hook.sh
+++ b/t/t0401-post-command-hook.sh
@@ -46,6 +46,67 @@ test_expect_success 'with failing pre-command hook' '
 	test_path_is_missing "$(cat .git/post-command.out)"
 '
 
+write_order_hooks () {
+	write_script .git/hooks/pre-command <<-EOF &&
+	echo "pre \$1" >>"$PWD/order.log"
+	if test "\$1" = git-vanish
+	then
+		rm -f "$PWD/bin/git-vanish"
+	fi
+	EOF
+	write_script .git/hooks/post-command <<-EOF
+	echo "post \$1" >>"$PWD/order.log"
+	EOF
+}
+
+test_expect_success 'post-command runs for a dashed external command' '
+	test_when_finished "rm -rf bin order.log .git/hooks/pre-command .git/hooks/post-command" &&
+	test_config postCommand.strategy always &&
+	write_order_hooks &&
+	mkdir bin &&
+	write_script bin/git-hello <<-\EOF &&
+	echo hello
+	EOF
+	PATH="$PWD/bin:$PATH" git hello &&
+	cat >expect <<-\EOF &&
+	pre git-hello
+	post git-hello
+	EOF
+	test_cmp expect order.log
+'
+
+test_expect_success 'post-command runs for a builtin that does not set up the repository' '
+	test_when_finished "rm -f order.log .git/hooks/pre-command .git/hooks/post-command" &&
+	test_config postCommand.strategy always &&
+	write_order_hooks &&
+	git version &&
+	cat >expect <<-\EOF &&
+	pre version
+	post version
+	EOF
+	test_cmp expect order.log
+'
+
+test_expect_success 'post-command runs when a dashed external vanishes before alias fallback' '
+	test_when_finished "rm -rf bin order.log .git/hooks/pre-command .git/hooks/post-command" &&
+	test_config postCommand.strategy always &&
+	test_config alias.vanish "rev-parse --git-dir" &&
+	write_order_hooks &&
+	mkdir bin &&
+	write_script bin/git-vanish <<-\EOF &&
+	echo vanish-script-ran
+	EOF
+	PATH="$PWD/bin:$PATH" git vanish >out &&
+	test_grep ! vanish-script-ran out &&
+	cat >expect <<-\EOF &&
+	pre git-vanish
+	post git-vanish
+	pre rev-parse
+	post rev-parse
+	EOF
+	test_cmp expect order.log
+'
+
 test_expect_success 'with post-index-change config' '
 	mkdir -p internal-hooks &&
 	write_script internal-hooks/post-command <<-EOF &&