Add merge-subtree back

An earlier commit e1b3a2c (Build-in merge-recursive) made the
subtree merge strategy backend unavailable.  This resurrects
it.

A new test t6029 currently only tests the strategy is available,
but it should be enhanced to check the real "subtree" case.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/t/t6029-merge-subtree.sh b/t/t6029-merge-subtree.sh
new file mode 100755
index 0000000000..3900a05082
--- /dev/null
+++ b/t/t6029-merge-subtree.sh
@@ -0,0 +1,32 @@
+#!/bin/sh
+
+test_description='subtree merge strategy'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+
+	s="1 2 3 4 5 6 7 8"
+	for i in $s; do echo $i; done >hello &&
+	git add hello &&
+	git commit -m initial &&
+	git checkout -b side &&
+	echo >>hello world &&
+	git add hello &&
+	git commit -m second &&
+	git checkout master &&
+	for i in mundo $s; do echo $i; done >hello &&
+	git add hello &&
+	git commit -m master
+
+'
+
+test_expect_success 'subtree available and works like recursive' '
+
+	git merge -s subtree side &&
+	for i in mundo $s world; do echo $i; done >expect &&
+	diff -u expect hello
+
+'
+
+test_done