hooks: allow customizing where the hook directory is

Change the hardcoded lookup for .git/hooks/* to optionally lookup in
$(git config core.hooksPath)/* instead.

This is essentially a more intrusive version of the git-init ability to
specify hooks on init time via init templates.

The difference between that facility and this feature is that this can
be set up after the fact via e.g. ~/.gitconfig or /etc/gitconfig to
apply for all your personal repositories, or all repositories on the
system.

I plan on using this on a centralized Git server where users can create
arbitrary repositories under /gitroot, but I'd like to manage all the
hooks that should be run centrally via a unified dispatch mechanism.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -618,6 +618,23 @@ core.attributesFile::
 	$XDG_CONFIG_HOME/git/attributes. If $XDG_CONFIG_HOME is either not
 	set or empty, $HOME/.config/git/attributes is used instead.
 
+core.hooksPath::
+	By default Git will look for your hooks in the
+	'$GIT_DIR/hooks' directory. Set this to different path,
+	e.g. '/etc/git/hooks', and Git will try to find your hooks in
+	that directory, e.g. '/etc/git/hooks/pre-receive' instead of
+	in '$GIT_DIR/hooks/pre-receive'.
++
+The path can be either absolute or relative. A relative path is
+taken as relative to the directory where the hooks are run (see
+the "DESCRIPTION" section of linkgit:githooks[5]).
++
+This configuration variable is useful in cases where you'd like to
+centrally configure your Git hooks instead of configuring them on a
+per-repository basis, or as a more flexible and centralized
+alternative to having an `init.templateDir` where you've changed
+default hooks.
+
 core.editor::
 	Commands such as `commit` and `tag` that lets you edit
 	messages by launching an editor uses the value of this

Documentation/githooks.txt

@@ -7,15 +7,19 @@ githooks - Hooks used by Git
 
 SYNOPSIS
 --------
-$GIT_DIR/hooks/*
+$GIT_DIR/hooks/* (or \`git config core.hooksPath`/*)
 
 
 DESCRIPTION
 -----------
 
-Hooks are programs you can place in the `$GIT_DIR/hooks` directory to
-trigger actions at certain points in git's execution. Hooks that don't
-have the executable bit set are ignored.
+Hooks are programs you can place in a hooks directory to trigger
+actions at certain points in git's execution. Hooks that don't have
+the executable bit set are ignored.
+
+By default the hooks directory is `$GIT_DIR/hooks`, but that can be
+changed via the `core.hooksPath` configuration variable (see
+linkgit:git-config[1]).
 
 Before Git invokes a hook, it changes its working directory to either
 the root of the working tree in a non-bare repository, or to the

cache.h

@@ -655,6 +655,7 @@ extern int shared_repository;
 extern const char *apply_default_whitespace;
 extern const char *apply_default_ignorewhitespace;
 extern const char *git_attributes_file;
+extern const char *git_hooks_path;
 extern int zlib_compression_level;
 extern int core_compression_level;
 extern int core_compression_seen;

config.c

@@ -717,6 +717,9 @@ static int git_default_core_config(const char *var, const char *value)
 	if (!strcmp(var, "core.attributesfile"))
 		return git_config_pathname(&git_attributes_file, var, value);
 
+	if (!strcmp(var, "core.hookspath"))
+		return git_config_pathname(&git_hooks_path, var, value);
+
 	if (!strcmp(var, "core.bare")) {
 		is_bare_repository_cfg = git_config_bool(var, value);
 		return 0;

environment.c

@@ -33,6 +33,7 @@ int shared_repository = PERM_UMASK;
 const char *apply_default_whitespace;
 const char *apply_default_ignorewhitespace;
 const char *git_attributes_file;
+const char *git_hooks_path;
 int zlib_compression_level = Z_BEST_SPEED;
 int core_compression_level;
 int core_compression_seen;

run-command.c

@@ -815,7 +815,10 @@ const char *find_hook(const char *name)
 	static struct strbuf path = STRBUF_INIT;
 
 	strbuf_reset(&path);
-	strbuf_git_path(&path, "hooks/%s", name);
+	if (git_hooks_path)
+		strbuf_addf(&path, "%s/%s", git_hooks_path, name);
+	else
+		strbuf_git_path(&path, "hooks/%s", name);
 	if (access(path.buf, X_OK) < 0)
 		return NULL;
 	return path.buf;

t/t1350-config-hooks-path.sh

@@ -0,0 +1,37 @@
+#!/bin/sh
+
+test_description='Test the core.hooksPath configuration variable'
+
+. ./test-lib.sh
+
+test_expect_success 'set up a pre-commit hook in core.hooksPath' '
+	mkdir -p .git/custom-hooks .git/hooks &&
+	write_script .git/custom-hooks/pre-commit <<-\EOF &&
+	echo CUSTOM >>actual
+	EOF
+	write_script .git/hooks/pre-commit <<-\EOF
+	echo NORMAL >>actual
+	EOF
+'
+
+test_expect_success 'Check that various forms of specifying core.hooksPath work' '
+	test_commit no_custom_hook &&
+	git config core.hooksPath .git/custom-hooks &&
+	test_commit have_custom_hook &&
+	git config core.hooksPath .git/custom-hooks/ &&
+	test_commit have_custom_hook_trailing_slash &&
+	git config core.hooksPath "$PWD/.git/custom-hooks" &&
+	test_commit have_custom_hook_abs_path &&
+	git config core.hooksPath "$PWD/.git/custom-hooks/" &&
+	test_commit have_custom_hook_abs_path_trailing_slash &&
+	cat >expect <<-\EOF &&
+	NORMAL
+	CUSTOM
+	CUSTOM
+	CUSTOM
+	CUSTOM
+	EOF
+	test_cmp expect actual
+'
+
+test_done