add test case for recursive merge

This test case is based on the bug report by Shawn Pearce.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

t/t6024-recursive-merge.sh

@@ -0,0 +1,70 @@
+#!/bin/sh
+
+test_description='Test merge without common ancestors'
+. ./test-lib.sh
+
+# This scenario is based on a real-world repository of Shawn Pearce.
+
+# 1 - A - D - F
+#   \   X   /
+#     B   X
+#       X   \
+# 2 - C - E - G
+
+export GIT_COMMITTER_DATE="2006-12-12 23:28:00 +0100"
+echo 1 > a1
+git add a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:00" git commit -m 1 a1
+
+git checkout -b A master
+echo A > a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:01" git commit -m A a1
+
+git checkout -b B master
+echo B > a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:02" git commit -m B a1
+
+git checkout -b D A
+git-rev-parse B > .git/MERGE_HEAD
+echo D > a1
+git update-index a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:03" git commit -m D
+
+git symbolic-ref HEAD refs/heads/other
+echo 2 > a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:04" git commit -m 2 a1
+
+git checkout -b C
+echo C > a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:05" git commit -m C a1
+
+git checkout -b E C
+git-rev-parse B > .git/MERGE_HEAD
+echo E > a1
+git update-index a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:06" git commit -m E
+
+git checkout -b G E
+git-rev-parse A > .git/MERGE_HEAD
+echo G > a1
+git update-index a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:07" git commit -m G
+
+git checkout -b F D
+git-rev-parse C > .git/MERGE_HEAD
+echo F > a1
+git update-index a1
+GIT_AUTHOR_DATE="2006-12-12 23:00:08" git commit -m F
+
+test_expect_failure "combined merge conflicts" "git merge -m final G"
+
+git ls-files --stage > out
+cat > expect << EOF
+100644 f70f10e4db19068f79bc43844b49f3eece45c4e8 1	a1
+100644 cf84443e49e1b366fac938711ddf4be2d4d1d9e9 2	a1
+100644 fd7923529855d0b274795ae3349c5e0438333979 3	a1
+EOF
+
+test_expect_success "virtual trees were processed" "diff -u expect out"
+
+test_done