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>

1 files changed, 10 insertions, 18 deletions

diff --git a/ref-filter.h b/ref-filter.h
index 6228458..aa0eea4 100644
--- a/ref-filter.h
+++ b/ref-filter.h
@@ -23,16 +23,13 @@
 #define FILTER_REFS_KIND_MASK      (FILTER_REFS_ALL | FILTER_REFS_DETACHED_HEAD)
 
 struct atom_value;
+struct ref_sorting;
 
-struct ref_sorting {
-	struct ref_sorting *next;
-	int atom; /* index into used_atom array (internal) */
-	enum {
-		REF_SORTING_REVERSE = 1<<0,
-		REF_SORTING_ICASE = 1<<1,
-		REF_SORTING_VERSION = 1<<2,
-		REF_SORTING_DETACHED_HEAD_FIRST = 1<<3,
-	} sort_flags;
+enum ref_sorting_order {
+	REF_SORTING_REVERSE = 1<<0,
+	REF_SORTING_ICASE = 1<<1,
+	REF_SORTING_VERSION = 1<<2,
+	REF_SORTING_DETACHED_HEAD_FIRST = 1<<3,
 };
 
 struct ref_array_item {
@@ -97,9 +94,8 @@ struct ref_format {
 #define OPT_NO_MERGED(f, h) _OPT_MERGED_NO_MERGED("no-merged", f, h)
 
 #define OPT_REF_SORT(var) \
-	OPT_CALLBACK_F(0, "sort", (var), \
-		       N_("key"), N_("field name to sort on"), \
-		       PARSE_OPT_NONEG, parse_opt_ref_sorting)
+	OPT_STRING_LIST(0, "sort", (var), \
+			N_("key"), N_("field name to sort on"))
 
 /*
  * API for filtering a set of refs. Based on the type of refs the user
@@ -121,14 +117,10 @@ int format_ref_array_item(struct ref_array_item *info,
 			  struct ref_format *format,
 			  struct strbuf *final_buf,
 			  struct strbuf *error_buf);
-/*  Parse a single sort specifier and add it to the list */
-void parse_ref_sorting(struct ref_sorting **sorting_tail, const char *atom);
-/*  Callback function for parsing the sort option */
-int parse_opt_ref_sorting(const struct option *opt, const char *arg, int unset);
-/*  Default sort option based on refname */
-struct ref_sorting *ref_default_sorting(void);
 /* Release a "struct ref_sorting" */
 void ref_sorting_release(struct ref_sorting *);
+/*  Convert list of sort options into ref_sorting */
+struct ref_sorting *ref_sorting_options(struct string_list *);
 /*  Function to parse --merged and --no-merged options */
 int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset);
 /*  Get the current HEAD's description */