filter-branch: eliminate duplicate mapped parents

diff --git a/t/t7003-filter-branch.sh b/t/t7003-filter-branch.sh
index 9496736a89eb6b0b1ece64052cd2726c516c952b..66643e4bd758aa55f4f58d70675e32f1ad173460 100755 (executable)
--- a/t/t7003-filter-branch.sh
+++ b/t/t7003-filter-branch.sh
@@ -308,6 +308,17 @@ test_expect_success 'Prune empty commits' '
        test_cmp expect actual
 '
 
+test_expect_success 'prune empty collapsed merges' '
+       test_config merge.ff false &&
+       git rev-list HEAD >expect &&
+       test_commit to_remove_2 &&
+       git reset --hard HEAD^ &&
+       test_merge non-ff to_remove_2 &&
+       git filter-branch -f --index-filter "git update-index --remove to_remove_2.t" --prune-empty HEAD &&
+       git rev-list HEAD >actual &&
+       test_cmp expect actual
+'
+
 test_expect_success '--remap-to-ancestor with filename filters' '
        git checkout master &&
        git reset --hard A &&