tag: support --sort=<spec>

--sort=version:refname (or --sort=v:refname for short) sorts tags as
if they are versions. --sort=-refname reverses the order (with or
without ":version").

versioncmp() is copied from string/strverscmp.c in glibc commit
ee9247c38a8def24a59eb5cfb7196a98bef8cfdc, reformatted to Git coding
style. The implementation is under LGPL-2.1 and according to [1] I can
relicense it to GPLv2.

[1] http://www.gnu.org/licenses/gpl-faq.html#AllCompatibility

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/t/t7004-tag.sh b/t/t7004-tag.sh
index c8d6e9f88..143a8ea60 100755
--- a/t/t7004-tag.sh
+++ b/t/t7004-tag.sh
@@ -1380,4 +1380,47 @@ test_expect_success 'multiple --points-at are OR-ed together' '
 	test_cmp expect actual
 '
 
+test_expect_success 'lexical sort' '
+	git tag foo1.3 &&
+	git tag foo1.6 &&
+	git tag foo1.10 &&
+	git tag -l --sort=refname "foo*" >actual &&
+	cat >expect <<EOF &&
+foo1.10
+foo1.3
+foo1.6
+EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'version sort' '
+	git tag -l --sort=version:refname "foo*" >actual &&
+	cat >expect <<EOF &&
+foo1.3
+foo1.6
+foo1.10
+EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'reverse version sort' '
+	git tag -l --sort=-version:refname "foo*" >actual &&
+	cat >expect <<EOF &&
+foo1.10
+foo1.6
+foo1.3
+EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'reverse lexical sort' '
+	git tag -l --sort=-refname "foo*" >actual &&
+	cat >expect <<EOF &&
+foo1.6
+foo1.3
+foo1.10
+EOF
+	test_cmp expect actual
+'
+
 test_done