string_list: add a new function, filter_string_list()

diff --git a/t/t1506-rev-parse-diagnosis.sh b/t/t1506-rev-parse-diagnosis.sh
index c5cb77a0e1f34ac46dd8727341948389624e8f38..f950c101287c2f05bbd70c1faffbcf2cda1edbee 100755 (executable)
--- a/t/t1506-rev-parse-diagnosis.sh
+++ b/t/t1506-rev-parse-diagnosis.sh
@@ -182,4 +182,18 @@ test_expect_success '<commit>:file correctly diagnosed after a pathname' '
        test_cmp expect actual
 '
 
+test_expect_success 'dotdot is not an empty set' '
+       ( H=$(git rev-parse HEAD) && echo $H && echo ^$H ) >expect &&
+
+       git rev-parse HEAD.. >actual &&
+       test_cmp expect actual &&
+
+       git rev-parse ..HEAD >actual &&
+       test_cmp expect actual &&
+
+       echo .. >expect &&
+       git rev-parse .. >actual &&
+       test_cmp expect actual
+'
+
 test_done