hook: introduce "git hook list"

If more than one hook will be run, it may be useful to see a list of
which hooks should be run. At very least, it will be useful for us to
test the semantics of multihooks ourselves.

For now, only list the hooks which will run in the order they will run
in; later, it might be useful to include more information like where the
hooks were configured and whether or not they will run.

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: nasamuffin

Documentation/git-hook.adoc

@@ -9,6 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git hook' run [--ignore-missing] [--to-stdin=<path>] <hook-name> [-- <hook-args>]
+'git hook' list <hook-name>
 
 DESCRIPTION
 -----------
@@ -28,6 +29,10 @@ Any positional arguments to the hook should be passed after a
 mandatory `--` (or `--end-of-options`, see linkgit:gitcli[7]). See
 linkgit:githooks[5] for arguments hooks might expect (if any).
 
+list::
+	Print a list of hooks which will be run on `<hook-name>` event. If no
+	hooks are configured for that event, print nothing and return 1.
+
 OPTIONS
 -------
 

builtin/hook.c

@@ -6,12 +6,16 @@
 #include "hook.h"
 #include "parse-options.h"
 #include "strvec.h"
+#include "abspath.h"
 
 #define BUILTIN_HOOK_RUN_USAGE \
 	N_("git hook run [--ignore-missing] [--to-stdin=<path>] <hook-name> [-- <hook-args>]")
+#define BUILTIN_HOOK_LIST_USAGE \
+	N_("git hook list <hook-name>")
 
 static const char * const builtin_hook_usage[] = {
 	BUILTIN_HOOK_RUN_USAGE,
+	BUILTIN_HOOK_LIST_USAGE,
 	NULL
 };
 
@@ -20,6 +24,54 @@ static const char * const builtin_hook_run_usage[] = {
 	NULL
 };
 
+static const char *const builtin_hook_list_usage[] = {
+	BUILTIN_HOOK_LIST_USAGE,
+	NULL
+};
+
+static int list(int argc, const char **argv, const char *prefix,
+		 struct repository *repo UNUSED)
+{
+	struct string_list *head;
+	struct string_list_item *item;
+	const char *hookname = NULL;
+	int ret = 0;
+
+	struct option list_options[] = {
+		OPT_END(),
+	};
+
+	argc = parse_options(argc, argv, prefix, list_options,
+			     builtin_hook_list_usage, 0);
+
+	/*
+	 * The only unnamed argument provided should be the hook-name; if we add
+	 * arguments later they probably should be caught by parse_options.
+	 */
+	if (argc != 1)
+		usage_msg_opt(_("You must specify a hook event name to list."),
+			      builtin_hook_list_usage, list_options);
+
+	hookname = argv[0];
+
+	head = list_hooks(the_repository, hookname);
+
+	if (!head->nr) {
+		ret = 1; /* no hooks found */
+		goto cleanup;
+	}
+
+	for_each_string_list_item(item, head) {
+		printf("%s\n", *item->string ? item->string
+			     : _("hook from hookdir"));
+	}
+
+cleanup:
+	string_list_clear(head, 1);
+	free(head);
+	return ret;
+}
+
 static int run(int argc, const char **argv, const char *prefix,
 	       struct repository *repo UNUSED)
 {
@@ -77,6 +129,7 @@ int cmd_hook(int argc,
 	parse_opt_subcommand_fn *fn = NULL;
 	struct option builtin_hook_options[] = {
 		OPT_SUBCOMMAND("run", &fn, run),
+		OPT_SUBCOMMAND("list", &fn, list),
 		OPT_END(),
 	};
 

hook.c

@@ -47,20 +47,7 @@ const char *find_hook(struct repository *r, const char *name)
 	return path.buf;
 }
 
-/*
- * Provides a list of hook commands to run for the 'hookname' event.
- *
- * This function consolidates hooks from two sources:
- * 1. The config-based hooks (not yet implemented).
- * 2. The "traditional" hook found in the repository hooks directory
- *    (e.g., .git/hooks/pre-commit).
- *
- * The list is ordered by execution priority.
- *
- * The caller is responsible for freeing the memory of the returned list
- * using string_list_clear() and free().
- */
-static struct string_list *list_hooks(struct repository *r, const char *hookname)
+struct string_list *list_hooks(struct repository *r, const char *hookname)
 {
 	struct string_list *hook_head;
 

hook.h

@@ -143,7 +143,22 @@ struct hook_cb_data {
 	struct repository *repository;
 };
 
-/*
+/**
+ * Provides a list of hook commands to run for the 'hookname' event.
+ *
+ * This function consolidates hooks from two sources:
+ * 1. The config-based hooks (not yet implemented).
+ * 2. The "traditional" hook found in the repository hooks directory
+ *    (e.g., .git/hooks/pre-commit).
+ *
+ * The list is ordered by execution priority.
+ *
+ * The caller is responsible for freeing the memory of the returned list
+ * using string_list_clear() and free().
+ */
+struct string_list *list_hooks(struct repository *r, const char *hookname);
+
+/**
  * Returns the path to the hook file, or NULL if the hook is missing
  * or disabled. Note that this points to static storage that will be
  * overwritten by further calls to find_hook and run_hook_*.

t/t1800-hook.sh

@@ -10,6 +10,8 @@ test_expect_success 'git hook usage' '
 	test_expect_code 129 git hook run &&
 	test_expect_code 129 git hook run -h &&
 	test_expect_code 129 git hook run --unknown 2>err &&
+	test_expect_code 129 git hook list &&
+	test_expect_code 129 git hook list -h &&
 	grep "unknown option" err
 '