ref-filter: apply --ignore-case to all sorting keys

All of the ref-filter users (for-each-ref, branch, and tag) take an
--ignore-case option which makes filtering and sorting case-insensitive.
However, this option was applied only to the first element of the
ref_sorting list. So:

  git for-each-ref --ignore-case --sort=refname

would do what you expect, but:

  git for-each-ref --ignore-case --sort=refname --sort=taggername

would sort the primary key (taggername) case-insensitively, but sort the
refname case-sensitively. We have two options here:

  - teach callers to set ignore_case on the whole list

  - replace the ref_sorting list with a struct that contains both the
    list of sorting keys, as well as options that apply to _all_
    keys

I went with the first one here, as it gives more flexibility if we later
want to let the users set the flag per-key (presumably through some
special syntax when defining the key; for now it's all or nothing
through --ignore-case).

The new test covers this by sorting on both tagger and subject
case-insensitively, which should compare "a" and "A" identically, but
still sort them before "b" and "B". We'll break ties by sorting on the
refname to give ourselves a stable output (this is actually supposed to
be done automatically, but there's another bug which will be fixed in
the next commit).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -711,7 +711,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		 */
 		if (!sorting)
 			sorting = ref_default_sorting();
-		sorting->ignore_case = icase;
+		ref_sorting_icase_all(sorting, icase);
 		print_ref_list(&filter, sorting, &format);
 		print_columns(&output, colopts, NULL);
 		string_list_clear(&output, 0);

builtin/for-each-ref.c

@@ -71,7 +71,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 
 	if (!sorting)
 		sorting = ref_default_sorting();
-	sorting->ignore_case = icase;
+	ref_sorting_icase_all(sorting, icase);
 	filter.ignore_case = icase;
 
 	filter.name_patterns = argv;

builtin/tag.c

@@ -465,7 +465,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	}
 	if (!sorting)
 		sorting = ref_default_sorting();
-	sorting->ignore_case = icase;
+	ref_sorting_icase_all(sorting, icase);
 	filter.ignore_case = icase;
 	if (cmdmode == 'l') {
 		int ret;

ref-filter.c

@@ -2163,6 +2163,12 @@ static int compare_refs(const void *a_, const void *b_, void *ref_sorting)
 	return 0;
 }
 
+void ref_sorting_icase_all(struct ref_sorting *sorting, int flag)
+{
+	for (; sorting; sorting = sorting->next)
+		sorting->ignore_case = !!flag;
+}
+
 void ref_array_sort(struct ref_sorting *sorting, struct ref_array *array)
 {
 	QSORT_S(array->items, array->nr, compare_refs, sorting);

ref-filter.h

@@ -109,6 +109,8 @@ void ref_array_clear(struct ref_array *array);
 int verify_ref_format(struct ref_format *format);
 /*  Sort the given ref_array as per the ref_sorting provided */
 void ref_array_sort(struct ref_sorting *sort, struct ref_array *array);
+/*  Set the ignore_case flag for all elements of a sorting list */
+void ref_sorting_icase_all(struct ref_sorting *sorting, int flag);
 /*  Based on the given format and quote_style, fill the strbuf */
 int format_ref_array_item(struct ref_array_item *info,
 			  const struct ref_format *format,

t/t6300-for-each-ref.sh

@@ -828,4 +828,44 @@ test_expect_success 'for-each-ref --ignore-case ignores case' '
 	test_cmp expect actual
 '
 
+test_expect_success 'for-each-ref --ignore-case works on multiple sort keys' '
+	# name refs numerically to avoid case-insensitive filesystem conflicts
+	nr=0 &&
+	for email in a A b B
+	do
+		for subject in a A b B
+		do
+			GIT_COMMITTER_EMAIL="$email@example.com" \
+			git tag -m "tag $subject" icase-$(printf %02d $nr) &&
+			nr=$((nr+1))||
+			return 1
+		done
+	done &&
+	git for-each-ref --ignore-case \
+		--format="%(taggeremail) %(subject) %(refname)" \
+		--sort=refname \
+		--sort=subject \
+		--sort=taggeremail \
+		refs/tags/icase-* >actual &&
+	cat >expect <<-\EOF &&
+	<a@example.com> tag a refs/tags/icase-00
+	<a@example.com> tag A refs/tags/icase-01
+	<A@example.com> tag a refs/tags/icase-04
+	<A@example.com> tag A refs/tags/icase-05
+	<a@example.com> tag b refs/tags/icase-02
+	<a@example.com> tag B refs/tags/icase-03
+	<A@example.com> tag b refs/tags/icase-06
+	<A@example.com> tag B refs/tags/icase-07
+	<b@example.com> tag a refs/tags/icase-08
+	<b@example.com> tag A refs/tags/icase-09
+	<B@example.com> tag a refs/tags/icase-12
+	<B@example.com> tag A refs/tags/icase-13
+	<b@example.com> tag b refs/tags/icase-10
+	<b@example.com> tag B refs/tags/icase-11
+	<B@example.com> tag b refs/tags/icase-14
+	<B@example.com> tag B refs/tags/icase-15
+	EOF
+	test_cmp expect actual
+'
+
 test_done