t4013: test "git log -m --stat"

This is to ensure we won't break different diff formats when we start
to imply "-p" by "-m".

Signed-off-by: Sergey Organov <sorganov@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4013-diff-various.sh

@@ -338,6 +338,7 @@ log -m -p master
 log --cc -m -p master
 log -c -m -p master
 log -m --raw master
+log -m --stat master
 log -SF master
 log -S F master
 log -SF -p master

t/t4013/diff.log_-m_--stat_master

@@ -0,0 +1,66 @@
+$ git log -m --stat master
+commit 59d314ad6f356dd08601a4cd5e530381da3e3c64 (from 9a6d4949b6b76956d9d5e26f2791ec2ceff5fdc0)
+Merge: 9a6d494 c7a2ab9
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:04:00 2006 +0000
+
+    Merge branch 'side'
+
+ dir/sub | 2 ++
+ file0   | 3 +++
+ 2 files changed, 5 insertions(+)
+
+commit 59d314ad6f356dd08601a4cd5e530381da3e3c64 (from c7a2ab9e8eac7b117442a607d5a9b3950ae34d5a)
+Merge: 9a6d494 c7a2ab9
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:04:00 2006 +0000
+
+    Merge branch 'side'
+
+ dir/sub | 4 ++++
+ file0   | 3 +++
+ file1   | 3 +++
+ file2   | 3 ---
+ file3   | 4 ----
+ 5 files changed, 10 insertions(+), 7 deletions(-)
+
+commit c7a2ab9e8eac7b117442a607d5a9b3950ae34d5a
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:03:00 2006 +0000
+
+    Side
+
+ dir/sub | 2 ++
+ file0   | 3 +++
+ file3   | 4 ++++
+ 3 files changed, 9 insertions(+)
+
+commit 9a6d4949b6b76956d9d5e26f2791ec2ceff5fdc0
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:02:00 2006 +0000
+
+    Third
+
+ dir/sub | 2 ++
+ file1   | 3 +++
+ 2 files changed, 5 insertions(+)
+
+commit 1bde4ae5f36c8d9abe3a0fce0c6aab3c4a12fe44
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:01:00 2006 +0000
+
+    Second
+    
+    This is the second commit.
+
+ dir/sub | 2 ++
+ file0   | 3 +++
+ file2   | 3 ---
+ 3 files changed, 5 insertions(+), 3 deletions(-)
+
+commit 444ac553ac7612cc88969031b02b3767fb8a353a
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:00:00 2006 +0000
+
+    Initial
+$