Subject: Re: [PATCH] submodule: implement `module_name` as a builtin helper

From: Jens Lehmann <[email-masked]>
Date: Thu, 6 Aug 2015 21:49:48 +0200

Am 05.08.2015 um 23:08 schrieb Stefan Beller:
> This implements the helper `module_name` in C instead of shell,
> yielding a nice performance boost.
>
> Before this patch, I measured a time (best out of three):
>
>    $ time ./t7400-submodule-basic.sh  >/dev/null
>      real	0m11.066s
>      user	0m3.348s
>      sys	0m8.534s
>
> With this patch applied I measured (also best out of three)
>
>    $ time ./t7400-submodule-basic.sh  >/dev/null
>      real	0m10.063s
>      user	0m3.044s
>      sys	0m7.487s
>
> Signed-off-by: Stefan Beller <[email-masked]>
> ---
>
> Is this what you had in mind, Jens?

Yup, thanks!

Just some small nits, please see below (and also in the fixup! commit
I pushed on the "submodule--helper" branch in my Github repo).

> Jonathan pointed me to https://github.com/jlehmann/git-submod-enhancements/wiki
> Does it reflect reality (i.e. as time passes code changes)?
 >
> I also noticed that you have made quite some changes to submodules on different
> branches which are not upstream. Soem changes look familiar (as in "I believe
> this is upstream alreaday?" while others look new and exciting to me).
> I could not quite get the order yet, though.

I think the Wiki should be pretty much up to date, but I'll try to check
that and the state of the branches on the weekend to see if it needs an
update. If you see some branches you believe are already upstream, it'd
be great if you could mention them so I can double check.

>   builtin/submodule--helper.c | 23 +++++++++++++++++++++++
>   git-submodule.sh            | 32 +++++++-------------------------
>   submodule.c                 | 18 +++++++++++++-----
>   submodule.h                 |  1 +
>   4 files changed, 44 insertions(+), 30 deletions(-)
>
> diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
> index cb18ddf..3713c4c 100644
> --- a/builtin/submodule--helper.c
> +++ b/builtin/submodule--helper.c
> @@ -5,6 +5,8 @@
>   #include "pathspec.h"
>   #include "dir.h"
>   #include "utf8.h"
> +#include "submodule.h"
> +#include "string-list.h"
>
>   static char *ps_matched;
>   static const struct cache_entry **ce_entries;
> @@ -98,6 +100,24 @@ static int module_list(int argc, const char **argv, const char *prefix)
>   	return 0;
>   }
>
> +static int module_name(int argc, const char **argv, const char *prefix)
> +{
> +	const char *name;
> +
> +	if (argc != 1)
> +		usage("git submodule--helper module_name <path>\n");
> +
> +	gitmodules_config();
> +	name = submodule_name_for_path(argv[0]);
> +
> +	if (name)
> +		printf("%s\n", name);
> +	else
> +		die("No submodule mapping found in .gitmodules for path '%s'", argv[0]);

Hmm, I prefer the pattern to bail out inside if() and continue with the
expected case without else:

+	if (!name)
+		die("No submodule mapping found in .gitmodules for path '%s'", argv[0]);
+
+	printf("%s\n", name);

But maybe that's just me.

> +	return 0;
> +}
> +
>   int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
>   {
>   	if (argc < 2)
> @@ -106,6 +126,9 @@ int cmd_submodule__helper(int argc, const char **argv, const char *prefix)
>   	if (!strcmp(argv[1], "module_list"))
>   		return module_list(argc - 1, argv + 1, prefix);
>
> +	if (!strcmp(argv[1], "module_name"))
> +		return module_name(argc - 2, argv + 2, prefix);
> +
>   usage:
>   	usage("git submodule--helper module_list\n");
>   }
> diff --git a/git-submodule.sh b/git-submodule.sh
> index af9ecef..e6ff38d 100755
> --- a/git-submodule.sh
> +++ b/git-submodule.sh
> @@ -178,24 +178,6 @@ get_submodule_config () {
>   	printf '%s' "${value:-$default}"
>   }
>
> -
> -#
> -# Map submodule path to submodule name
> -#
> -# $1 = path
> -#
> -module_name()
> -{
> -	# Do we have "submodule.<something>.path = $1" defined in .gitmodules file?
> -	sm_path="$1"
> -	re=$(printf '%s\n' "$1" | sed -e 's/[].[^$\\*]/\\&/g')
> -	name=$( git config -f .gitmodules --get-regexp '^submodule\..*\.path$' |
> -		sed -n -e 's|^submodule\.\(.*\)\.path '"$re"'$|\1|p' )
> -	test -z "$name" &&
> -	die "$(eval_gettext "No submodule mapping found in .gitmodules for path '\$sm_path'")"
> -	printf '%s\n' "$name"
> -}
> -
>   #
>   # Clone a submodule
>   #
> @@ -498,7 +480,7 @@ cmd_foreach()
>   		then
>   			displaypath=$(relative_path "$sm_path")
>   			say "$(eval_gettext "Entering '\$prefix\$displaypath'")"
> -			name=$(module_name "$sm_path")
> +			name=$(git submodule--helper module_name "$sm_path")
>   			(
>   				prefix="$prefix$sm_path/"
>   				clear_local_git_env
> @@ -554,7 +536,7 @@ cmd_init()
>   	while read mode sha1 stage sm_path
>   	do
>   		die_if_unmatched "$mode"
> -		name=$(module_name "$sm_path") || exit
> +		name=$(git submodule--helper module_name "$sm_path") || exit
>
>   		displaypath=$(relative_path "$sm_path")
>
> @@ -636,7 +618,7 @@ cmd_deinit()
>   	while read mode sha1 stage sm_path
>   	do
>   		die_if_unmatched "$mode"
> -		name=$(module_name "$sm_path") || exit
> +		name=$(git submodule--helper module_name "$sm_path") || exit
>
>   		displaypath=$(relative_path "$sm_path")
>
> @@ -758,7 +740,7 @@ cmd_update()
>   			echo >&2 "Skipping unmerged submodule $prefix$sm_path"
>   			continue
>   		fi
> -		name=$(module_name "$sm_path") || exit
> +		name=$(git submodule--helper module_name "$sm_path") || exit
>   		url=$(git config submodule."$name".url)
>   		branch=$(get_submodule_config "$name" branch master)
>   		if ! test -z "$update"
> @@ -1022,7 +1004,7 @@ cmd_summary() {
>   			# Respect the ignore setting for --for-status.
>   			if test -n "$for_status"
>   			then
> -				name=$(module_name "$sm_path")
> +				name=$(git submodule--helper module_name "$sm_path")
>   				ignore_config=$(get_submodule_config "$name" ignore none)
>   				test $status != A && test $ignore_config = all && continue
>   			fi
> @@ -1184,7 +1166,7 @@ cmd_status()
>   	while read mode sha1 stage sm_path
>   	do
>   		die_if_unmatched "$mode"
> -		name=$(module_name "$sm_path") || exit
> +		name=$(git submodule--helper module_name "$sm_path") || exit
>   		url=$(git config submodule."$name".url)
>   		displaypath=$(relative_path "$prefix$sm_path")
>   		if test "$stage" = U
> @@ -1261,7 +1243,7 @@ cmd_sync()
>   	while read mode sha1 stage sm_path
>   	do
>   		die_if_unmatched "$mode"
> -		name=$(module_name "$sm_path")
> +		name=$(git submodule--helper module_name "$sm_path")
>   		url=$(git config -f .gitmodules --get submodule."$name".url)
>
>   		# Possibly a url relative to parent
> diff --git a/submodule.c b/submodule.c
> index 700bbf4..dd8dcb0 100644
> --- a/submodule.c
> +++ b/submodule.c
> @@ -686,6 +686,16 @@ static void calculate_changed_submodule_paths(void)
>   	initialized_fetch_ref_tips = 0;
>   }
>
> +const char* submodule_name_for_path(const char* path)

Asterisk belongs to the name, not the type:

+const char *submodule_name_for_path(const char *path)

> +{
> +	struct string_list_item *item;
> +	item = unsorted_string_list_lookup(&config_name_for_path, path);
> +	if (item)
> +		return item->util;
> +	else
> +		return NULL;

Maybe we could use the "if() bailout;" pattern here too:

+	if (!item)
+		return NULL;
+
+	return item->util;

("else" after "return" looks strange ;-)

> +}
> +
>   int fetch_populated_submodules(const struct argv_array *options,
>   			       const char *prefix, int command_line_option,
>   			       int quiet)
> @@ -693,7 +703,7 @@ int fetch_populated_submodules(const struct argv_array *options,
>   	int i, result = 0;
>   	struct child_process cp = CHILD_PROCESS_INIT;
>   	struct argv_array argv = ARGV_ARRAY_INIT;
> -	struct string_list_item *name_for_path;
> +	const char *name_for_path;
>   	const char *work_tree = get_git_work_tree();
>   	if (!work_tree)
>   		goto out;
> @@ -723,10 +733,8 @@ int fetch_populated_submodules(const struct argv_array *options,
>   		if (!S_ISGITLINK(ce->ce_mode))
>   			continue;
>
> -		name = ce->name;
> -		name_for_path = unsorted_string_list_lookup(&config_name_for_path, ce->name);
> -		if (name_for_path)
> -			name = name_for_path->util;
> +		name_for_path = submodule_name_for_path(ce->name);
> +		name =  name_for_path ? name_for_path : ce->name;

I think we can get rid of name_for_path auto variable altogether here.
(And while at it why not add the previously missing comment why we do
fall back to the path here?):

+		name = submodule_name_for_path(ce->name);
+		if (!name)
+			/* Not in .gitmodules, try the default name == path */
+			name = ce->name;

>   		default_argv = "yes";
>   		if (command_line_option == RECURSE_SUBMODULES_DEFAULT) {
> diff --git a/submodule.h b/submodule.h
> index 7beec48..e3dd854 100644
> --- a/submodule.h
> +++ b/submodule.h
> @@ -41,5 +41,6 @@ int find_unpushed_submodules(unsigned char new_sha1[20], const char *remotes_nam
>   		struct string_list *needs_pushing);
>   int push_unpushed_submodules(unsigned char new_sha1[20], const char *remotes_name);
>   void connect_work_tree_and_git_dir(const char *work_tree, const char *git_dir);
> +const char* submodule_name_for_path(const char* path);

Asterisk belongs to the names, not the type here too.

+const char *submodule_name_for_path(const char *path);

>   #endif