merge-tree: support multiple batched merges with --stdin

Add an option, --stdin, to merge-tree which will accept lines of input
with two branches to merge per line, and which will perform all the
merges and give output for each in turn.  This option implies -z, and
modifies the output to also include a merge status since the exit code
of the program can no longer convey that information now that multiple
merges are involved.

This could be useful, for example, by Git hosting providers.  When one
branch is updated, one may want to check whether all code reviews
targetting that branch can still cleanly merge.  Avoiding the overhead
of starting up a separate process for each of those code reviews might
provide significant savings in a repository with many code reviews.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/t/t4301-merge-tree-write-tree.sh b/t/t4301-merge-tree-write-tree.sh
index 013b77144b..cac85591b5 100755
--- a/t/t4301-merge-tree-write-tree.sh
+++ b/t/t4301-merge-tree-write-tree.sh
@@ -819,4 +819,45 @@ test_expect_success SANITY 'merge-ort fails gracefully in a read-only repository
 	test_must_fail git -C read-only merge-tree side1 side2
 '
 
+test_expect_success '--stdin with both a successful and a conflicted merge' '
+	printf "side1 side3\nside1 side2" | git merge-tree --stdin >actual &&
+
+	git checkout side1^0 &&
+	git merge side3 &&
+
+	printf "1\0" >expect &&
+	git rev-parse HEAD^{tree} | lf_to_nul >>expect &&
+	printf "\0" >>expect &&
+
+	git checkout side1^0 &&
+	test_must_fail git merge side2 &&
+	sed s/HEAD/side1/ greeting >tmp &&
+	mv tmp greeting &&
+	git add -u &&
+	git mv whatever~HEAD whatever~side1 &&
+
+	printf "0\0" >>expect &&
+	git write-tree | lf_to_nul >>expect &&
+
+	cat <<-EOF | q_to_tab | lf_to_nul >>expect &&
+	100644 $(git rev-parse side1~1:greeting) 1Qgreeting
+	100644 $(git rev-parse side1:greeting) 2Qgreeting
+	100644 $(git rev-parse side2:greeting) 3Qgreeting
+	100644 $(git rev-parse side1~1:whatever) 1Qwhatever~side1
+	100644 $(git rev-parse side1:whatever) 2Qwhatever~side1
+	EOF
+
+	q_to_nul <<-EOF >>expect &&
+	Q1QgreetingQAuto-mergingQAuto-merging greeting
+	Q1QgreetingQCONFLICT (contents)QCONFLICT (content): Merge conflict in greeting
+	Q1QnumbersQAuto-mergingQAuto-merging numbers
+	Q2Qwhatever~side1QwhateverQCONFLICT (file/directory)QCONFLICT (file/directory): directory in the way of whatever from side1; moving it to whatever~side1 instead.
+	Q1Qwhatever~side1QCONFLICT (modify/delete)QCONFLICT (modify/delete): whatever~side1 deleted in side2 and modified in side1.  Version side1 of whatever~side1 left in tree.
+	EOF
+
+	printf "\0\0" >>expect &&
+
+	test_cmp expect actual
+'
+
 test_done