t4013: test "git diff-tree -m"

We want to ensure we don't affect plumbing commands with our changes
of "-m" semantics, so add corresponding test.

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

t/t4013-diff-various.sh

@@ -293,6 +293,7 @@ diff-tree --stat initial mode
 diff-tree --summary initial mode
 
 diff-tree master
+diff-tree -m master
 diff-tree -p master
 diff-tree -p -m master
 diff-tree -c master

t/t4013/diff.diff-tree_-m_master

@@ -0,0 +1,11 @@
+$ git diff-tree -m master
+59d314ad6f356dd08601a4cd5e530381da3e3c64
+:040000 040000 65f5c9dd60ce3b2b3324b618ac7accf8d912c113 0564e026437809817a64fff393079714b6dd4628 M	dir
+:100644 100644 b414108e81e5091fe0974a1858b4d0d22b107f70 10a8a9f3657f91a156b9f0184ed79a20adef9f7f M	file0
+59d314ad6f356dd08601a4cd5e530381da3e3c64
+:040000 040000 f977ed46ae6873c1c30ab878e15a4accedc3618b 0564e026437809817a64fff393079714b6dd4628 M	dir
+:100644 100644 f4615da674c09df322d6ba8d6b21ecfb1b1ba510 10a8a9f3657f91a156b9f0184ed79a20adef9f7f M	file0
+:000000 100644 0000000000000000000000000000000000000000 b1e67221afe8461efd244b487afca22d46b95eb8 A	file1
+:100644 000000 01e79c32a8c99c557f0757da7cb6d65b3414466d 0000000000000000000000000000000000000000 D	file2
+:100644 000000 7289e35bff32727c08dda207511bec138fdb9ea5 0000000000000000000000000000000000000000 D	file3
+$