Subject: Re: [GSoC][PATCH 13/13] submodule: port submodule subcommand 'foreach' from shell to C

From: Brandon Williams <[email-masked]>
Date: Mon, 24 Jul 2017 17:29:24 -0700

On 07/25, Prathamesh Chavan wrote:
> This aims to make git-submodule foreach a builtin. This is the very
> first step taken in this direction. Hence, 'foreach' is ported to
> submodule--helper, and submodule--helper is called from git-submodule.sh.
> The code is split up to have one function to obtain all the list of
> submodules. This function acts as the front-end of git-submodule foreach
> subcommand. It calls the function for_each_submodule_list, which basically
> loops through the list and calls function fn, which in this case is
> runcommand_in_submodule. This third function is a calling function that
> takes care of running the command in that submodule, and recursively
> perform the same when --recursive is flagged.
> 
> The first function module_foreach first parses the options present in
> argv, and then with the help of module_list_compute, generates the list of
> submodules present in the current working tree.
> 
> The second function for_each_submodule_list traverses through the
> list, and calls function fn (which in case of submodule subcommand
> foreach is runcommand_in_submodule) is called for each entry.
> 
> The third function runcommand_in_submodule, generates a submodule struct sub
> for $name, value and then later prepends name=sub->name; and other
> value assignment to the env argv_array structure of a child_process.
> Also the <command> of submodule-foreach is push to args argv_array
> structure and finally, using run_command the commands are executed
> using a shell.
> 
> The third function also takes care of the recursive flag, by creating
> a separate child_process structure and prepending "--super-prefix displaypath",
> to the args argv_array structure. Other required arguments and the
> input <command> of submodule-foreach is also appended to this argv_array.
> 
> Helped-by: Brandon Williams <[email-masked]>
> Mentored-by: Christian Couder <[email-masked]>
> Mentored-by: Stefan Beller <[email-masked]>
> Signed-off-by: Prathamesh Chavan <[email-masked]>
> ---
>  builtin/submodule--helper.c | 129 ++++++++++++++++++++++++++++++++++++++++++++
>  git-submodule.sh            |  39 +-------------
>  2 files changed, 130 insertions(+), 38 deletions(-)
> 
> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index 94d6254f0..be278bf8d 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -765,6 +765,134 @@ static int module_name(int argc, const char **argv, const char *prefix)
>  	return 0;
>  }
>  
> +struct cb_foreach {
> +	int argc;
> +	const char **argv;
> +	const char *prefix;
> +	unsigned int quiet: 1;
> +	unsigned int recursive: 1;
> +};
> +#define CB_FOREACH_INIT { 0, NULL, NULL, 0, 0 }
> +
> +static void runcommand_in_submodule(const struct cache_entry *list_item,
> +				    void *cb_data)
> +{
> +	struct cb_foreach *info = cb_data;
> +	const struct submodule *sub;
> +	struct child_process cp = CHILD_PROCESS_INIT;
> +	char *displaypath;
> +
> +	displaypath = get_submodule_displaypath(list_item->name, info->prefix);
> +
> +	sub = submodule_from_path(null_sha1, list_item->name);
> +
> +	if (!sub)
> +		die(_("No url found for submodule path '%s' in .gitmodules"),
> +		      displaypath);
> +
> +	if (!is_submodule_populated_gently(list_item->name, NULL))
> +		goto cleanup;
> +
> +	prepare_submodule_repo_env(&cp.env_array);
> +	/* For the purpose of executing <command> in the submodule,
> +	 * separate shell is used for the purpose of running the
> +	 * child process.
> +	 */

comment style

> +	cp.use_shell = 1;
> +	cp.dir = list_item->name;
> +
> +	if (info->argc == 1) {

Why are you only exposing these variables if argc == 1?

> +		char *toplevel = xgetcwd();
> +
> +		argv_array_pushf(&cp.env_array, "name=%s", sub->name);
> +		argv_array_pushf(&cp.env_array, "sm_path=%s", list_item->name);
> +		argv_array_pushf(&cp.env_array, "displaypath=%s", displaypath);
> +		argv_array_pushf(&cp.env_array, "sha1=%s",
> +				 oid_to_hex(&list_item->oid));
> +		argv_array_pushf(&cp.env_array, "toplevel=%s", toplevel);
> +
> +		/*
> +		 * Since still the path variable was accessible from the
> +		 * script before porting, it is also made available.
> +		 */
> +		argv_array_pushf(&cp.args, "path=%s; %s",
> +				 list_item->name, info->argv[0]);

This bit looks odd. Why are you appending argv[0] after a semicolon?
Oh...its to handle the funny path stuff.  I'd add a comment indicating
why you have to expose path  via the args argv_array and not the
env_array.

> +		free(toplevel);
> +	} else {
> +		argv_array_pushv(&cp.args, info->argv);
> +	}
> +
> +	if (!info->quiet)
> +		printf(_("Entering '%s'\n"), displaypath);
> +
> +	if (info->argv[0] && run_command(&cp))
> +		die(_("run_command returned non-zero status for %s\n."),
> +		      displaypath);
> +
> +	if (info->recursive) {
> +		struct child_process cpr = CHILD_PROCESS_INIT;
> +
> +		cpr.git_cmd = 1;
> +		cpr.dir = list_item->name;
> +		prepare_submodule_repo_env(&cpr.env_array);
> +
> +		argv_array_pushl(&cpr.args, "--super-prefix", displaypath,

Same comment as a few of the other commands about super-prefix.

> +				 "submodule--helper", "foreach", "--recursive",
> +				 NULL);
> +
> +		if (info->quiet)
> +			argv_array_push(&cpr.args, "--quiet");
> +
> +		argv_array_pushv(&cpr.args, info->argv);
> +
> +		if (run_command(&cpr))
> +			die(_("run_command returned non-zero status while"
> +			      "recursing in the nested submodules of %s\n."),
> +			      displaypath);
> +	}
> +
> +cleanup:
> +	free(displaypath);
> +}
> +
> +static int module_foreach(int argc, const char **argv, const char *prefix)
> +{
> +	struct cb_foreach info;
> +	struct pathspec pathspec;
> +	struct module_list list = MODULE_LIST_INIT;
> +	int quiet = 0;
> +	int recursive = 0;
> +
> +	struct option module_foreach_options[] = {
> +		OPT__QUIET(&quiet, N_("Suppress output of entering each submodule command")),
> +		OPT_BOOL(0, "recursive", &recursive,
> +			 N_("Recurse into nested submodules")),
> +		OPT_END()
> +	};
> +
> +	const char *const git_submodule_helper_usage[] = {
> +		N_("git submodule--helper foreach [--quiet] [--recursive] <command>"),
> +		NULL
> +	};
> +
> +	argc = parse_options(argc, argv, prefix, module_foreach_options,
> +			     git_submodule_helper_usage, PARSE_OPT_KEEP_UNKNOWN);
> +
> +	if (module_list_compute(0, NULL, prefix, &pathspec, &list) < 0)
> +		BUG("module_list_compute should not choke on empty pathspec");
> +
> +	info.argc = argc;
> +	info.argv = argv;
> +	info.prefix = prefix;
> +	info.quiet = !!quiet;
> +	info.recursive = !!recursive;
> +
> +	gitmodules_config();
> +	for_each_submodule_list(list, runcommand_in_submodule, &info);
> +
> +	return 0;
> +}
> +
>  struct module_cb {
>  	unsigned int mod_src;
>  	unsigned int mod_dst;
> @@ -2203,6 +2331,7 @@ static struct cmd_struct commands[] = {
>  	{"resolve-relative-url", resolve_relative_url, 0},
>  	{"resolve-relative-url-test", resolve_relative_url_test, 0},
>  	{"print-name-rev", print_name_rev, 0},
> +	{"foreach", module_foreach, SUPPORT_SUPER_PREFIX},
>  	{"init", module_init, SUPPORT_SUPER_PREFIX},
>  	{"status", module_status, SUPPORT_SUPER_PREFIX},
>  	{"print-default-remote", print_default_remote, 0},
> diff --git a/git-submodule.sh b/git-submodule.sh
> index 493a64372..e25b2c613 100755
> --- a/git-submodule.sh
> +++ b/git-submodule.sh
> @@ -298,44 +298,7 @@ cmd_foreach()
>  		shift
>  	done
>  
> -	toplevel=$(pwd)
> -
> -	# dup stdin so that it can be restored when running the external
> -	# command in the subshell (and a recursive call to this function)
> -	exec 3<&0
> -
> -	{
> -		git submodule--helper list --prefix "$wt_prefix" ||
> -		echo "#unmatched" $?
> -	} |
> -	while read -r mode sha1 stage sm_path
> -	do
> -		die_if_unmatched "$mode" "$sha1"
> -		if test -e "$sm_path"/.git
> -		then
> -			displaypath=$(git submodule--helper relative-path "$prefix$sm_path" "$wt_prefix")
> -			say "$(eval_gettext "Entering '\$displaypath'")"
> -			name=$(git submodule--helper name "$sm_path")
> -			(
> -				prefix="$prefix$sm_path/"
> -				sanitize_submodule_env
> -				cd "$sm_path" &&
> -				# we make $path available to scripts ...
> -				path=$sm_path &&
> -				if test $# -eq 1
> -				then
> -					eval "$1"
> -				else
> -					"$@"
> -				fi &&
> -				if test -n "$recursive"
> -				then
> -					cmd_foreach "--recursive" "$@"
> -				fi
> -			) <&3 3<&- ||
> -			die "$(eval_gettext "Stopping at '\$displaypath'; script returned non-zero status.")"
> -		fi
> -	done
> +	git ${wt_prefix:+-C "$wt_prefix"} ${prefix:+--super-prefix "$prefix"} submodule--helper foreach ${GIT_QUIET:+--quiet} ${recursive:+--recursive} "$@"
>  }
>  
>  #
> -- 
> 2.13.0
> 

-- 
Brandon Williams