[PATCH 6/9] submodule: helper to run foreach in parallel

[Stefan Beller <sbeller@google.com>]

Similar to `git submodule foreach` the new command `git submodule
foreach_parallel` will run a command on each submodule.

The commands are run in parallel up to the number of cores by default,
or you can specify '-j 4' tun just run with 4 threads for example.

One major difference to `git submodule foreach` is the handling of input
and output to the commands. Because of the parallel nature of the execution
it is not trivial how to schedule the std{in,out,err} channel for submodule
the command is run in. So in this patch there is no support for stdin.
stdout will be piped to stderr. stderr will make use of the synchronized
output feature of run_command.

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 builtin/submodule--helper.c  | 133 ++++++++++++++++++++++++++++++++++++++++++-
 git-submodule.sh             |  11 +++-
 t/t7407-submodule-foreach.sh |  11 ++++
 3 files changed, 153 insertions(+), 2 deletions(-)

diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index d29499c..18b67f0 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -8,6 +8,7 @@
 #include "submodule.h"
 #include "submodule-config.h"
 #include "string-list.h"
+#include "thread-utils.h"
 #include "run-command.h"
 
 static const struct cache_entry **ce_entries;
@@ -266,6 +267,127 @@ static int module_clone(int argc, const char **argv, const char *prefix)
 	return 0;
 }
 
+#ifndef NO_PTHREADS
+struct submodule_args {
+	const char *name;
+	const char *path;
+	const char *sha1;
+	const char *toplevel;
+	const char *prefix;
+	const char **cmd;
+	pthread_mutex_t *sync;
+};
+
+int run_cmd_submodule(struct task_queue *aq, void *task)
+{
+	int i;
+	struct submodule_args *args = task;
+	struct strbuf out = STRBUF_INIT;
+	struct strbuf sb = STRBUF_INIT;
+	struct child_process *cp = xmalloc(sizeof(*cp));
+
+	strbuf_addf(&out, N_("Entering %s\n"), relative_path(args->path, args->prefix, &sb));
+
+	child_process_init(cp);
+	argv_array_pushv(&cp->args, args->cmd);
+
+	argv_array_pushf(&cp->env_array, "name=%s", args->name);
+	argv_array_pushf(&cp->env_array, "path=%s", args->path);
+	argv_array_pushf(&cp->env_array, "sha1=%s", args->sha1);
+	argv_array_pushf(&cp->env_array, "toplevel=%s", args->toplevel);
+
+	for (i = 0; local_repo_env[i]; i++)
+		argv_array_push(&cp->env_array, local_repo_env[i]);
+
+	cp->no_stdin = 1;
+	cp->out = 0;
+	cp->err = -1;
+	cp->dir = args->path;
+	cp->stdout_to_stderr = 1;
+	cp->use_shell = 1;
+	cp->sync_mutex = args->sync;
+	cp->sync_buf = &out;
+
+	return run_command(cp);
+}
+
+int module_foreach_parallel(int argc, const char **argv, const char *prefix)
+{
+	int i, recursive = 0, number_threads = 0, quiet = 0;
+	static struct pathspec pathspec;
+	struct strbuf sb = STRBUF_INIT;
+	struct task_queue *aq;
+	char **cmd;
+	const char **nullargv = {NULL};
+	pthread_mutex_t mutex;
+
+	struct option module_update_options[] = {
+		OPT_STRING(0, "prefix", &alternative_path,
+			   N_("path"),
+			   N_("alternative anchor for relative paths")),
+		OPT_STRING(0, "cmd", &cmd,
+			   N_("string"),
+			   N_("command to run")),
+		OPT_BOOL('r', "--recursive", &recursive,
+			 N_("Recurse into nexted submodules")),
+		OPT_INTEGER('j', "jobs", &number_threads,
+			    N_("Recurse into nexted submodules")),
+		OPT__QUIET(&quiet, N_("Suppress output")),
+		OPT_END()
+	};
+
+	static const char * const git_submodule_helper_usage[] = {
+		N_("git submodule--helper foreach [--prefix=<path>] [<path>...]"),
+		NULL
+	};
+
+	argc = parse_options(argc, argv, prefix, module_update_options,
+			     git_submodule_helper_usage, 0);
+
+	if (module_list_compute(0, nullargv, NULL, &pathspec) < 0)
+		return 1;
+
+	gitmodules_config();
+
+	pthread_mutex_init(&mutex, NULL);
+	aq = create_task_queue(number_threads);
+
+	for (i = 0; i < ce_used; i++) {
+		const struct submodule *sub;
+		const struct cache_entry *ce = ce_entries[i];
+		struct submodule_args *args = malloc(sizeof(*args));
+
+		if (ce_stage(ce))
+			args->sha1 = xstrdup(sha1_to_hex(null_sha1));
+		else
+			args->sha1 = xstrdup(sha1_to_hex(ce->sha1));
+
+		strbuf_reset(&sb);
+		strbuf_addf(&sb, "%s/.git", ce->name);
+		if (!file_exists(sb.buf)) {
+			free(args);
+			continue;
+		}
+
+		args->path = ce->name;
+		sub = submodule_from_path(null_sha1, args->path);
+		if (!sub)
+			die("No submodule mapping found in .gitmodules for path '%s'", args->path);
+
+		args->name = sub->name;
+		args->toplevel = xgetcwd();
+		args->cmd = argv;
+		args->sync = &mutex;
+		args->prefix = alternative_path;
+		add_task(aq, run_cmd_submodule, args);
+	}
+
+	finish_task_queue(aq, NULL);
+	pthread_mutex_destroy(&mutex);
+	return 0;
+}
+#endif /* NO_PTHREADS */
+
 int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
 {
 	if (argc < 2)
@@ -280,7 +402,16 @@ int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
 	if (!strcmp(argv[1], "module_clone"))
 		return module_clone(argc - 1, argv + 1, prefix);
 
+#ifndef NO_PTHREADS
+	if (!strcmp(argv[1], "foreach_parallel"))
+		return module_foreach_parallel(argc - 1, argv + 1, prefix);
+#endif
+
 usage:
 	usage("git submodule--helper [module_list | module_name | "
-	      "module_clone]\n");
+	      "module_clone"
+#ifndef NO_PTHREADS
+	      " | foreach_parallel"
+#endif
+	      "]\n");
 }
diff --git a/git-submodule.sh b/git-submodule.sh
index fb5155e..f06488a 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -431,6 +431,15 @@ cmd_foreach()
 }
 
 #
+# Execute an arbitrary command sequence in each checked out
+# submodule in parallel.
+#
+cmd_foreach_parallel()
+{
+	git submodule--helper foreach_parallel --prefix "$wt_prefix" $@
+}
+
+#
 # Register submodules in .git/config
 #
 # $@ = requested paths (default to all)
@@ -1225,7 +1234,7 @@ cmd_sync()
 while test $# != 0 && test -z "$command"
 do
 	case "$1" in
-	add | foreach | init | deinit | update | status | summary | sync)
+	add | foreach | foreach_parallel | init | deinit | update | status | summary | sync)
 		command=$1
 		;;
 	-q|--quiet)
diff --git a/t/t7407-submodule-foreach.sh b/t/t7407-submodule-foreach.sh
index 7ca10b8..16f6138 100755
--- a/t/t7407-submodule-foreach.sh
+++ b/t/t7407-submodule-foreach.sh
@@ -195,6 +195,17 @@ test_expect_success 'test "foreach --quiet --recursive"' '
 	test_cmp expect actual
 '
 
+test_expect_success 'test "foreach_parallel --quiet"' '
+	(
+		cd clone2 &&
+		git submodule foreach_parallel -q -- "echo \$name-\$path" > ../actual
+	) &&
+	grep nested1-nested1 actual &&
+	grep foo1-sub1 actual &&
+	grep foo2-sub2 actual &&
+	grep foo3-sub3 actual
+'
+
 test_expect_success 'use "update --recursive" to checkout all submodules' '
 	git clone super clone3 &&
 	(
-- 
2.5.0.264.g5e52b0d