diff: use second filename for --stat reporting on git patches (issue4221)

mercurial/patch.py

@@ -1859,7 +1859,7 b' def diffstatdata(lines):'
             # set numbers to 0 anyway when starting new file
             adds, removes, isbinary = 0, 0, False
             if line.startswith('diff --git a/'):
-                filename = gitre.search(line).group(1)
+                filename = gitre.search(line).group(2)
             elif line.startswith('diff -r'):
                 # format: "diff -r ... -r ... filename"
                 filename = diffre.search(line).group(1)

tests/test-glog.t

@@ -1853,7 +1853,7 b' Test --patch and --stat with --follow an'
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     copy a b
   |
-  |   a |  0
+  |   b |  0
   |   1 files changed, 0 insertions(+), 0 deletions(-)
   |
 
@@ -1886,7 +1886,7 b' Test --patch and --stat with --follow an'
   |  date:        Thu Jan 01 00:00:00 1970 +0000
   |  summary:     copy a b
   |
-  |   a |  0
+  |   b |  0
   |   1 files changed, 0 insertions(+), 0 deletions(-)
   |
   o  changeset:   0:f8035bb17114