add: remove support for git-legacy-stash

In 90a6bb9 (legacy stash -p: respect the add.interactive.usebuiltin
setting, 2019-12-21), we added support to use the built-in `add -p` from
the scripted `stash -p`.

In 8a2cd3f (stash: remove the stash.useBuiltin setting, 2020-03-03),
we retired the scripted `stash` (including the scripted `stash -p`).

Therefore this support is no longer necessary.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/add.c

@@ -32,7 +32,6 @@ static int add_renormalize;
 static int pathspec_file_nul;
 static int include_sparse;
 static const char *pathspec_from_file;
-static int legacy_stash_p; /* support for the scripted `git stash` */
 
 struct update_callback_data {
 	int flags;
@@ -388,8 +387,6 @@ static struct option builtin_add_options[] = {
 		   N_("override the executable bit of the listed files")),
 	OPT_HIDDEN_BOOL(0, "warn-embedded-repo", &warn_on_embedded_repo,
 			N_("warn when adding an embedded repository")),
-	OPT_HIDDEN_BOOL(0, "legacy-stash-p", &legacy_stash_p,
-			N_("backend for `git stash -p`")),
 	OPT_PATHSPEC_FROM_FILE(&pathspec_from_file),
 	OPT_PATHSPEC_FILE_NUL(&pathspec_file_nul),
 	OPT_END(),
@@ -512,17 +509,6 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 			die(_("options '%s' and '%s' cannot be used together"), "--pathspec-from-file", "--interactive/--patch");
 		exit(interactive_add(argv + 1, prefix, patch_interactive));
 	}
-	if (legacy_stash_p) {
-		struct pathspec pathspec;
-
-		parse_pathspec(&pathspec, 0,
-			PATHSPEC_PREFER_FULL |
-			PATHSPEC_SYMLINK_LEADING_PATH |
-			PATHSPEC_PREFIX_ORIGIN,
-			prefix, argv);
-
-		return run_add_interactive(NULL, "--patch=stash", &pathspec);
-	}
 
 	if (edit_interactive) {
 		if (pathspec_from_file)