Subject: [RFC PATCH v3 6/6] hook: add 'run' subcommand

From: Emily Shaffer <[email-masked]>
Date: Tue, 28 Jul 2020 15:24:55 -0700

In order to enable hooks to be run as an external process, by a
standalone Git command, or by tools which wrap Git, provide an external
means to run all configured hook commands for a given hook event.

For now, the hook commands will in config order, in series. As alternate
ordering or parallelism is supported in the future, we should add knobs
to use those to the command line as well.

As with the legacy hook implementation, all stdout generated by hook
commands is redirected to stderr. Piping from stdin is not yet
supported.

Legacy hooks (those present in $GITDIR/hooks) are run at the end of the
execution list. For now, there is no way to disable them.

Users may wish to provide hook commands like 'git config
hook.pre-commit.command "~/linter.sh --pre-commit"'. To enable this, the
contents of the 'hook.*.command' and 'hookcmd.*.command' strings are
first split by space or quotes into an argv_array, then expanded with
'expand_user_path()'.

Signed-off-by: Emily Shaffer <[email-masked]>
---
 builtin/hook.c                | 30 +++++++++++++++++++++++++
 hook.c                        | 42 +++++++++++++++++++++++++++++++++++
 hook.h                        |  3 +++
 t/t1360-config-based-hooks.sh | 28 +++++++++++++++++++++++
 4 files changed, 103 insertions(+)

diff --git a/builtin/hook.c b/builtin/hook.c
index 0d92124ca6..cd61fad5fb 100644
--- a/builtin/hook.c
+++ b/builtin/hook.c
@@ -5,9 +5,11 @@
 #include "hook.h"
 #include "parse-options.h"
 #include "strbuf.h"
+#include "argv-array.h"
 
 static const char * const builtin_hook_usage[] = {
 	N_("git hook list <hookname>"),
+	N_("git hook run [(-e|--env)=<var>...] [(-a|--arg)=<arg>...] <hookname>"),
 	NULL
 };
 
@@ -62,6 +64,32 @@ static int list(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+static int run(int argc, const char **argv, const char *prefix)
+{
+	struct strbuf hookname = STRBUF_INIT;
+	struct argv_array env_argv = ARGV_ARRAY_INIT;
+	struct argv_array arg_argv = ARGV_ARRAY_INIT;
+
+	struct option run_options[] = {
+		OPT_ARGV_ARRAY('e', "env", &env_argv, N_("var"),
+			       N_("environment variables for hook to use")),
+		OPT_ARGV_ARRAY('a', "arg", &arg_argv, N_("args"),
+			       N_("argument to pass to hook")),
+		OPT_END(),
+	};
+
+	argc = parse_options(argc, argv, prefix, run_options,
+			     builtin_hook_usage, 0);
+
+	if (argc < 1)
+		usage_msg_opt(_("a hookname must be provided to operate on."),
+			      builtin_hook_usage, run_options);
+
+	strbuf_addstr(&hookname, argv[0]);
+
+	return run_hooks(env_argv.argv, &hookname, &arg_argv);
+}
+
 int cmd_hook(int argc, const char **argv, const char *prefix)
 {
 	struct option builtin_hook_options[] = {
@@ -72,6 +100,8 @@ int cmd_hook(int argc, const char **argv, const char *prefix)
 
 	if (!strcmp(argv[1], "list"))
 		return list(argc - 1, argv + 1, prefix);
+	if (!strcmp(argv[1], "run"))
+		return run(argc - 1, argv + 1, prefix);
 
 	usage_with_options(builtin_hook_usage, builtin_hook_options);
 }
diff --git a/hook.c b/hook.c
index 9dfc1a885e..902e213173 100644
--- a/hook.c
+++ b/hook.c
@@ -2,6 +2,7 @@
 
 #include "hook.h"
 #include "config.h"
+#include "run-command.h"
 
 static LIST_HEAD(hook_head);
 
@@ -78,6 +79,7 @@ static int hook_config_lookup(const char *key, const char *value, void *hook_key
 struct list_head* hook_list(const struct strbuf* hookname)
 {
 	struct strbuf hook_key = STRBUF_INIT;
+	const char *legacy_hook_path = NULL;
 
 	if (!hookname)
 		return NULL;
@@ -86,5 +88,45 @@ struct list_head* hook_list(const struct strbuf* hookname)
 
 	git_config(hook_config_lookup, (void*)hook_key.buf);
 
+	legacy_hook_path = find_hook(hookname->buf);
+
+	/* TODO: check hook.runHookDir */
+	if (legacy_hook_path)
+		emplace_hook(&hook_head, legacy_hook_path);
+
 	return &hook_head;
 }
+
+int run_hooks(const char *const *env, const struct strbuf *hookname,
+	      const struct argv_array *args)
+{
+	struct list_head *to_run, *pos = NULL, *tmp = NULL;
+	int rc = 0;
+
+	to_run = hook_list(hookname);
+
+	list_for_each_safe(pos, tmp, to_run) {
+		struct child_process hook_proc = CHILD_PROCESS_INIT;
+		struct hook *hook = list_entry(pos, struct hook, list);
+
+		/* add command */
+		argv_array_push(&hook_proc.args, hook->command.buf);
+
+		/*
+		 * add passed-in argv, without expanding - let the user get back
+		 * exactly what they put in
+		 */
+		if (args)
+			argv_array_pushv(&hook_proc.args, args->argv);
+
+		hook_proc.env = env;
+		hook_proc.no_stdin = 1;
+		hook_proc.stdout_to_stderr = 1;
+		hook_proc.trace2_hook_name = hook->command.buf;
+		hook_proc.use_shell = 1;
+
+		rc |= run_command(&hook_proc);
+	}
+
+	return rc;
+}
diff --git a/hook.h b/hook.h
index aaf6511cff..cf598d6ccb 100644
--- a/hook.h
+++ b/hook.h
@@ -1,6 +1,7 @@
 #include "config.h"
 #include "list.h"
 #include "strbuf.h"
+#include "argv-array.h"
 
 struct hook
 {
@@ -10,6 +11,8 @@ struct hook
 };
 
 struct list_head* hook_list(const struct strbuf *hookname);
+int run_hooks(const char *const *env, const struct strbuf *hookname,
+	      const struct argv_array *args);
 
 void free_hook(struct hook *ptr);
 void clear_hook_list(void);
diff --git a/t/t1360-config-based-hooks.sh b/t/t1360-config-based-hooks.sh
index ebf8f38d68..ee8114250d 100755
--- a/t/t1360-config-based-hooks.sh
+++ b/t/t1360-config-based-hooks.sh
@@ -84,4 +84,32 @@ test_expect_success 'git hook list --porcelain prints just the command' '
 	test_cmp expected actual
 '
 
+test_expect_success 'inline hook definitions execute oneliners' '
+	test_config hook.pre-commit.command "echo \"Hello World\"" &&
+
+	echo "Hello World" >expected &&
+
+	# hooks are run with stdout_to_stderr = 1
+	git hook run pre-commit 2>actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'inline hook definitions resolve paths' '
+	cat >~/sample-hook.sh <<-EOF &&
+	echo \"Sample Hook\"
+	EOF
+
+	test_when_finished "rm ~/sample-hook.sh" &&
+
+	chmod +x ~/sample-hook.sh &&
+
+	test_config hook.pre-commit.command "~/sample-hook.sh" &&
+
+	echo \"Sample Hook\" >expected &&
+
+	# hooks are run with stdout_to_stderr = 1
+	git hook run pre-commit 2>actual &&
+	test_cmp expected actual
+'
+
 test_done
-- 
2.28.0.rc0.142.g3c755180ce-goog