for-each-ref: delay parsing of --sort=<atom> options

The for-each-ref family of commands invoke parsers immediately when
it sees each --sort=<atom> option, and die before even seeing the
other options on the command line when the <atom> is unrecognised.

Instead, accumulate them in a string list, and have them parsed into
a ref_sorting structure after the command line parsing is done.  As
a consequence, "git branch --sort=bogus -h" used to fail to give the
brief help, which arguably may have been a feature, now does so,
which is more consistent with how other options work.

The patch is smaller than the actual extent of the "damage" to the
codebase, thanks to the fact that the original code consistently
used OPT_REF_SORT() macro to handle command line options.  We only
needed to replace the variable used for the list, and implementation
of the callback function used in the macro.

The old rule was for the users of the API to:

 - Declare ref_sorting and ref_sorting_tail variables;

 - OPT_REF_SORT() macro will instantiate ref_sorting instance (which
   may barf and die) and append it to the tail;

 - Append to the tail each ref_sorting read from the configuration
   by parsing in the config callback (which may barf and die);

 - See if ref_sorting is null and use ref_sorting_default() instead.

Now the rule is not all that different but is simpler:

 - Declare ref_sorting_options string list.

 - OPT_REF_SORT() macro will append it to the string list;

 - Append to the string list the sort key read from the
   configuration;

 - call ref_sorting_options() to turn the string list to ref_sorting
   structure (which also deals with the default value).

As side effects, this change also cleans up a few issues:

 - 95be717c (parse_opt_ref_sorting: always use with NONEG flag,
   2019-03-20) muses that "git for-each-ref --no-sort" should simply
   clear the sort keys accumulated so far; it now does.

 - The implementation detail of "struct ref_sorting" and the helper
   function parse_ref_sorting() can now be private to the ref-filter
   API implementation.

 - If you set branch.sort to a bogus value, the any "git branch"
   invocation, not only the listing mode, would abort with the
   original code; now it doesn't

Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 24 insertions, 23 deletions

diff --git a/builtin/branch.c b/builtin/branch.c
index 7a1d1eeb07..81b5c111cb 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -77,12 +77,11 @@ define_list_config_array(color_branch_slots);
 static int git_branch_config(const char *var, const char *value, void *cb)
 {
 	const char *slot_name;
-	struct ref_sorting **sorting_tail = (struct ref_sorting **)cb;
 
 	if (!strcmp(var, "branch.sort")) {
 		if (!value)
 			return config_error_nonbool(var);
-		parse_ref_sorting(sorting_tail, value);
+		string_list_append(cb, value);
 		return 0;
 	}
 
@@ -625,7 +624,8 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	enum branch_track track;
 	struct ref_filter filter;
 	int icase = 0;
-	static struct ref_sorting *sorting = NULL, **sorting_tail = &sorting;
+	static struct ref_sorting *sorting;
+	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 	struct ref_format format = REF_FORMAT_INIT;
 
 	struct option options[] = {
@@ -666,7 +666,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		OPT_MERGED(&filter, N_("print only branches that are merged")),
 		OPT_NO_MERGED(&filter, N_("print only branches that are not merged")),
 		OPT_COLUMN(0, "column", &colopts, N_("list branches in columns")),
-		OPT_REF_SORT(sorting_tail),
+		OPT_REF_SORT(&sorting_options),
 		OPT_CALLBACK(0, "points-at", &filter.points_at, N_("object"),
 			N_("print only branches of the object"), parse_opt_object_name),
 		OPT_BOOL('i', "ignore-case", &icase, N_("sorting and filtering are case insensitive")),
@@ -683,7 +683,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_branch_usage, options);
 
-	git_config(git_branch_config, sorting_tail);
+	git_config(git_branch_config, &sorting_options);
 
 	track = git_branch_track;
 
@@ -749,8 +749,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		 * local branches 'refs/heads/...' and finally remote-tracking
 		 * branches 'refs/remotes/...'.
 		 */
-		if (!sorting)
-			sorting = ref_default_sorting();
+		sorting = ref_sorting_options(&sorting_options);
 		ref_sorting_set_sort_flags_all(sorting, REF_SORTING_ICASE, icase);
 		ref_sorting_set_sort_flags_all(
 			sorting, REF_SORTING_DETACHED_HEAD_FIRST, 1);
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 16a2c7d57c..6f62f40d12 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -17,7 +17,8 @@ static char const * const for_each_ref_usage[] = {
 int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 {
 	int i;
-	struct ref_sorting *sorting = NULL, **sorting_tail = &sorting;
+	struct ref_sorting *sorting;
+	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 	int maxcount = 0, icase = 0;
 	struct ref_array array;
 	struct ref_filter filter;
@@ -39,7 +40,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 		OPT_INTEGER( 0 , "count", &maxcount, N_("show only <n> matched refs")),
 		OPT_STRING(  0 , "format", &format.format, N_("format"), N_("format to use for the output")),
 		OPT__COLOR(&format.use_color, N_("respect format colors")),
-		OPT_REF_SORT(sorting_tail),
+		OPT_REF_SORT(&sorting_options),
 		OPT_CALLBACK(0, "points-at", &filter.points_at,
 			     N_("object"), N_("print only refs which points at the given object"),
 			     parse_opt_object_name),
@@ -70,8 +71,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	if (verify_ref_format(&format))
 		usage_with_options(for_each_ref_usage, opts);
 
-	if (!sorting)
-		sorting = ref_default_sorting();
+	sorting = ref_sorting_options(&sorting_options);
 	ref_sorting_set_sort_flags_all(sorting, REF_SORTING_ICASE, icase);
 	filter.ignore_case = icase;
 
diff --git a/builtin/ls-remote.c b/builtin/ls-remote.c
index 318949c3d7..44448fa61d 100644
--- a/builtin/ls-remote.c
+++ b/builtin/ls-remote.c
@@ -54,7 +54,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 	struct transport *transport;
 	const struct ref *ref;
 	struct ref_array ref_array;
-	static struct ref_sorting *sorting = NULL, **sorting_tail = &sorting;
+	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 
 	struct option options[] = {
 		OPT__QUIET(&quiet, N_("do not print remote URL")),
@@ -68,7 +68,7 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 		OPT_BIT(0, "refs", &flags, N_("do not show peeled tags"), REF_NORMAL),
 		OPT_BOOL(0, "get-url", &get_url,
 			 N_("take url.<base>.insteadOf into account")),
-		OPT_REF_SORT(sorting_tail),
+		OPT_REF_SORT(&sorting_options),
 		OPT_SET_INT_F(0, "exit-code", &status,
 			      N_("exit with exit code 2 if no matching refs are found"),
 			      2, PARSE_OPT_NOCOMPLETE),
@@ -86,8 +86,6 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 
 	packet_trace_identity("ls-remote");
 
-	UNLEAK(sorting);
-
 	if (argc > 1) {
 		int i;
 		CALLOC_ARRAY(pattern, argc);
@@ -139,8 +137,13 @@ int cmd_ls_remote(int argc, const char **argv, const char *prefix)
 		item->symref = xstrdup_or_null(ref->symref);
 	}
 
-	if (sorting)
+	if (sorting_options.nr) {
+		struct ref_sorting *sorting;
+
+		sorting = ref_sorting_options(&sorting_options);
 		ref_array_sort(sorting, &ref_array);
+		ref_sorting_release(sorting);
+	}
 
 	for (i = 0; i < ref_array.nr; i++) {
 		const struct ref_array_item *ref = ref_array.items[i];
diff --git a/builtin/tag.c b/builtin/tag.c
index 6fe646710d..41863c5ab7 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -178,7 +178,6 @@ static const char tag_template_nocleanup[] =
 static int git_tag_config(const char *var, const char *value, void *cb)
 {
 	int status;
-	struct ref_sorting **sorting_tail = (struct ref_sorting **)cb;
 
 	if (!strcmp(var, "tag.gpgsign")) {
 		config_sign_tag = git_config_bool(var, value);
@@ -188,7 +187,7 @@ static int git_tag_config(const char *var, const char *value, void *cb)
 	if (!strcmp(var, "tag.sort")) {
 		if (!value)
 			return config_error_nonbool(var);
-		parse_ref_sorting(sorting_tail, value);
+		string_list_append(cb, value);
 		return 0;
 	}
 
@@ -436,7 +435,8 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	struct ref_transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 	struct ref_filter filter;
-	static struct ref_sorting *sorting = NULL, **sorting_tail = &sorting;
+	struct ref_sorting *sorting;
+	struct string_list sorting_options = STRING_LIST_INIT_DUP;
 	struct ref_format format = REF_FORMAT_INIT;
 	int icase = 0;
 	int edit_flag = 0;
@@ -470,7 +470,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		OPT_WITHOUT(&filter.no_commit, N_("print only tags that don't contain the commit")),
 		OPT_MERGED(&filter, N_("print only tags that are merged")),
 		OPT_NO_MERGED(&filter, N_("print only tags that are not merged")),
-		OPT_REF_SORT(sorting_tail),
+		OPT_REF_SORT(&sorting_options),
 		{
 			OPTION_CALLBACK, 0, "points-at", &filter.points_at, N_("object"),
 			N_("print only tags of the object"), PARSE_OPT_LASTARG_DEFAULT,
@@ -486,7 +486,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 
 	setup_ref_filter_porcelain_msg();
 
-	git_config(git_tag_config, sorting_tail);
+	git_config(git_tag_config, &sorting_options);
 
 	memset(&opt, 0, sizeof(opt));
 	memset(&filter, 0, sizeof(filter));
@@ -525,8 +525,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 			die(_("--column and -n are incompatible"));
 		colopts = 0;
 	}
-	if (!sorting)
-		sorting = ref_default_sorting();
+	sorting = ref_sorting_options(&sorting_options);
 	ref_sorting_set_sort_flags_all(sorting, REF_SORTING_ICASE, icase);
 	filter.ignore_case = icase;
 	if (cmdmode == 'l') {