unpack-trees.c: look ahead in the index

diff --git a/t/t6010-merge-base.sh b/t/t6010-merge-base.sh
index 79124ec761a90fd0e2f028b4566fd21947ba5490..0144d9e858d2d8bf1720331c52f1809ed36e81b0 100755 (executable)
--- a/t/t6010-merge-base.sh
+++ b/t/t6010-merge-base.sh
@@ -149,6 +149,12 @@ test_expect_success 'merge-base A B C' '
        test "$MM1" = "$MB"
 '
 
+test_expect_success 'merge-base A B C using show-branch' '
+       MB=$(git show-branch --merge-base MMA MMB MMC) &&
+       MMR=$(git rev-parse --verify MMR) &&
+       test "$MMR" = "$MB"
+'
+
 test_expect_success 'criss-cross merge-base for octopus-step (setup)' '
        git reset --hard MMR &&
        test_tick && git commit --allow-empty -m 1 && git tag CC1 &&