Merge branch 'js/difftool-no-index'

"git difftool" can now run outside a repository.

* js/difftool-no-index:
  difftool: allow running outside Git worktrees with --no-index
  parse-options: make OPT_ARGUMENT() more useful
  difftool: remove obsolete (and misleading) comment

Documentation/technical/api-parse-options.txt

@@ -198,8 +198,10 @@ There are some macros to easily define options:
 	The filename will be prefixed by passing the filename along with
 	the prefix argument of `parse_options()` to `prefix_filename()`.
 
-`OPT_ARGUMENT(long, description)`::
+`OPT_ARGUMENT(long, &int_var, description)`::
 	Introduce a long-option argument that will be kept in `argv[]`.
+	If this option was seen, `int_var` will be set to one (except
+	if a `NULL` pointer was passed).
 
 `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`::
 	Recognize numerical options like -123 and feed the integer as

builtin/difftool.c

@@ -690,7 +690,7 @@ static int run_file_diff(int prompt, const char *prefix,
 int cmd_difftool(int argc, const char **argv, const char *prefix)
 {
 	int use_gui_tool = 0, dir_diff = 0, prompt = -1, symlinks = 0,
-	    tool_help = 0;
+	    tool_help = 0, no_index = 0;
 	static char *difftool_cmd = NULL, *extcmd = NULL;
 	struct option builtin_difftool_options[] = {
 		OPT_BOOL('g', "gui", &use_gui_tool,
@@ -714,6 +714,7 @@ int cmd_difftool(int argc, const char **argv, const char *prefix)
 			    "tool returns a non - zero exit code")),
 		OPT_STRING('x', "extcmd", &extcmd, N_("command"),
 			   N_("specify a custom command for viewing diffs")),
+		OPT_ARGUMENT("no-index", &no_index, N_("passed to `diff`")),
 		OPT_END()
 	};
 
@@ -727,9 +728,14 @@ int cmd_difftool(int argc, const char **argv, const char *prefix)
 	if (tool_help)
 		return print_tool_help();
 
-	/* NEEDSWORK: once we no longer spawn anything, remove this */
-	setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
-	setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
+	if (!no_index && !startup_info->have_repository)
+		die(_("difftool requires worktree or --no-index"));
+
+	if (!no_index){
+		setup_work_tree();
+		setenv(GIT_DIR_ENVIRONMENT, absolute_path(get_git_dir()), 1);
+		setenv(GIT_WORK_TREE_ENVIRONMENT, absolute_path(get_git_work_tree()), 1);
+	}
 
 	if (use_gui_tool && diff_gui_tool && *diff_gui_tool)
 		setenv("GIT_DIFF_TOOL", diff_gui_tool, 1);

git.c

@@ -498,7 +498,7 @@ static struct cmd_struct commands[] = {
 	{ "diff-files", cmd_diff_files, RUN_SETUP | NEED_WORK_TREE | NO_PARSEOPT },
 	{ "diff-index", cmd_diff_index, RUN_SETUP | NO_PARSEOPT },
 	{ "diff-tree", cmd_diff_tree, RUN_SETUP | NO_PARSEOPT },
-	{ "difftool", cmd_difftool, RUN_SETUP | NEED_WORK_TREE },
+	{ "difftool", cmd_difftool, RUN_SETUP_GENTLY },
 	{ "fast-export", cmd_fast_export, RUN_SETUP },
 	{ "fetch", cmd_fetch, RUN_SETUP },
 	{ "fetch-pack", cmd_fetch_pack, RUN_SETUP | NO_PARSEOPT },

parse-options.c

@@ -288,6 +288,8 @@ again:
 					     optname(options, flags));
 			if (*rest)
 				continue;
+			if (options->value)
+				*(int *)options->value = options->defval;
 			p->out[p->cpidx++] = arg - 2;
 			return PARSE_OPT_DONE;
 		}

parse-options.h

@@ -140,8 +140,8 @@ struct option {
 #define OPT_INTEGER_F(s, l, v, h, f)     { OPTION_INTEGER, (s), (l), (v), N_("n"), (h), (f) }
 
 #define OPT_END()                   { OPTION_END }
-#define OPT_ARGUMENT(l, h)          { OPTION_ARGUMENT, 0, (l), NULL, NULL, \
-				      (h), PARSE_OPT_NOARG}
+#define OPT_ARGUMENT(l, v, h)       { OPTION_ARGUMENT, 0, (l), (v), NULL, \
+				      (h), PARSE_OPT_NOARG, NULL, 1 }
 #define OPT_GROUP(h)                { OPTION_GROUP, 0, NULL, NULL, NULL, (h) }
 #define OPT_BIT(s, l, v, h, b)      OPT_BIT_F(s, l, v, h, b, 0)
 #define OPT_BITOP(s, l, v, h, set, clear) { OPTION_BITOP, (s), (l), (v), NULL, (h), \

t/helper/test-parse-options.c

@@ -132,7 +132,7 @@ int cmd__parse_options(int argc, const char **argv)
 		OPT_NOOP_NOARG(0, "obsolete"),
 		OPT_STRING_LIST(0, "list", &list, "str", "add str to list"),
 		OPT_GROUP("Magic arguments"),
-		OPT_ARGUMENT("quux", "means --quux"),
+		OPT_ARGUMENT("quux", NULL, "means --quux"),
 		OPT_NUMBER_CALLBACK(&integer, "set integer to NUM",
 			number_callback),
 		{ OPTION_COUNTUP, '+', NULL, &boolean, NULL, "same as -b",

t/t7800-difftool.sh

@@ -705,4 +705,14 @@ test_expect_success SYMLINKS 'difftool --dir-diff handles modified symlinks' '
 	test_cmp expect actual
 '
 
+test_expect_success 'outside worktree' '
+	echo 1 >1 &&
+	echo 2 >2 &&
+	test_expect_code 1 nongit git \
+		-c diff.tool=echo -c difftool.echo.cmd="echo \$LOCAL \$REMOTE" \
+		difftool --no-prompt --no-index ../1 ../2 >actual &&
+	echo "../1 ../2" >expect &&
+	test_cmp expect actual
+'
+
 test_done