[PATCH 04/12] grep: add a test for backreferences in PCRE patterns

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Add a test for backreferences such as (.)\1 in PCRE patterns. This
test ensures that the PCRE_NO_AUTO_CAPTURE option isn't turned
on. Before this change turning it on would break these sort of
patterns, but wouldn't break any tests.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 t/t7810-grep.sh | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index 53c2ca05c4..83b0ee53be 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -1102,6 +1102,13 @@ test_expect_success LIBPCRE 'grep -P -w pattern' '
 	test_cmp expected actual
 '
 
+test_expect_success PCRE 'grep -P backreferences work (the PCRE NO_AUTO_CAPTURE flag is not set)' '
+	git grep -P -h "(?P<one>.)(?P=one)" hello_world >actual &&
+	test_cmp hello_world actual &&
+	git grep -P -h "(.)\1" hello_world >actual &&
+	test_cmp hello_world actual
+'
+
 test_expect_success 'grep -G invalidpattern properly dies ' '
 	test_must_fail git grep -G "a["
 '
-- 
2.11.0