legacy stash -p: respect the add.interactive.usebuiltin setting

As `git add` traditionally did not expose the `--patch=<mode>` modes via
command-line options, the scripted version of `git stash` had to call
`git add--interactive` directly.

But this prevents the built-in `add -p` from kicking in, as
`add--interactive` is the Perl script.

So let's introduce support for an optional `<mode>` argument in `git add
--patch[=<mode>]`, and use that in the scripted version of `git stash
-p`, so that the built-in interactive add can do its job if configured.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

builtin/add.c

@@ -26,7 +26,8 @@ static const char * const builtin_add_usage[] = {
 	N_("git add [<options>] [--] <pathspec>..."),
 	NULL
 };
-static int patch_interactive, add_interactive, edit_interactive;
+static const char *patch_interactive;
+static int add_interactive, edit_interactive;
 static int take_worktree_changes;
 static int add_renormalize;
 
@@ -228,9 +229,11 @@ int run_add_interactive(const char *revision, const char *patch_mode,
 	return status;
 }
 
-int interactive_add(int argc, const char **argv, const char *prefix, int patch)
+int interactive_add(int argc, const char **argv, const char *prefix,
+		    const char *patch_mode)
 {
 	struct pathspec pathspec;
+	char buffer[64];
 
 	parse_pathspec(&pathspec, 0,
 		       PATHSPEC_PREFER_FULL |
@@ -238,9 +241,13 @@ int interactive_add(int argc, const char **argv, const char *prefix, int patch)
 		       PATHSPEC_PREFIX_ORIGIN,
 		       prefix, argv);
 
-	return run_add_interactive(NULL,
-				   patch ? "--patch" : NULL,
-				   &pathspec);
+	if (patch_mode) {
+		xsnprintf(buffer, sizeof(buffer), "--patch%s%s",
+			  *patch_mode ? "=" : "", patch_mode);
+		patch_mode = buffer;
+	}
+
+	return run_add_interactive(NULL, patch_mode, &pathspec);
 }
 
 static int edit_patch(int argc, const char **argv, const char *prefix)
@@ -318,7 +325,9 @@ static struct option builtin_add_options[] = {
 	OPT__VERBOSE(&verbose, N_("be verbose")),
 	OPT_GROUP(""),
 	OPT_BOOL('i', "interactive", &add_interactive, N_("interactive picking")),
-	OPT_BOOL('p', "patch", &patch_interactive, N_("select hunks interactively")),
+	{ OPTION_STRING, 'p', "patch", &patch_interactive, N_("patch-mode"),
+		N_("select hunks interactively"), PARSE_OPT_OPTARG, NULL,
+		(intptr_t) "" },
 	OPT_BOOL('e', "edit", &edit_interactive, N_("edit current diff and apply")),
 	OPT__FORCE(&ignored_too, N_("allow adding otherwise ignored files"), 0),
 	OPT_BOOL('u', "update", &take_worktree_changes, N_("update tracked files")),

builtin/commit.c

@@ -358,7 +358,8 @@ static const char *prepare_index(int argc, const char **argv, const char *prefix
 		old_index_env = xstrdup_or_null(getenv(INDEX_ENVIRONMENT));
 		setenv(INDEX_ENVIRONMENT, get_lock_file_path(&index_lock), 1);
 
-		if (interactive_add(argc, argv, prefix, patch_interactive) != 0)
+		if (interactive_add(argc, argv, prefix,
+				    patch_interactive ? "" : NULL) != 0)
 			die(_("interactive add failed"));
 
 		if (old_index_env && *old_index_env)

commit.h

@@ -295,7 +295,8 @@ int delayed_reachability_test(struct shallow_info *si, int c);
 void prune_shallow(unsigned options);
 extern struct trace_key trace_shallow;
 
-int interactive_add(int argc, const char **argv, const char *prefix, int patch);
+int interactive_add(int argc, const char **argv, const char *prefix,
+		    const char *patch_mode);
 int run_add_interactive(const char *revision, const char *patch_mode,
 			const struct pathspec *pathspec);
 

git-legacy-stash.sh

@@ -206,7 +206,7 @@ create_stash () {
 
 		# find out what the user wants
 		GIT_INDEX_FILE="$TMP-index" \
-			git add--interactive --patch=stash -- "$@" &&
+			git add --patch=stash -- "$@" &&
 
 		# state of the working tree
 		w_tree=$(GIT_INDEX_FILE="$TMP-index" git write-tree) ||