Turn on git diff copy detection for git-cl upload.

Enable copy detection for git-cl upload.  This makes
it possible to copy a directory containing many files,
add+commit the new path, and then upload a patch to
Rietveld that shows the files were copied.

In my tests, -C -C was needed to pick up a basic
file copy.  -C was not enough.  I'm not sure why
exactly.  The output generated in the diff looks
like:

  sh$ git diff -C -C HEAD~1..HEAD
  diff --git a/slave/Makefile b/slave2/Makefile
  similarity index 100%
  copy from slave/Makefile
  copy to slave2/Makefile
  ...

(This change requires r141676 /
https://chromiumcodereview.appspot.com/10543116/ which
updates upload.py to use --find-copies-harder.)

R=maruel@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10545107

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@141689 0039d316-1c4b-4281-b951-d872f2087c98

git_cl.py

@@ -1128,7 +1128,8 @@ def CMDupload(parser, args):
   if 'GIT_EXTERNAL_DIFF' in env:
     del env['GIT_EXTERNAL_DIFF']
   subprocess2.call(
-      ['git', 'diff', '--no-ext-diff', '--stat', '-M'] + args, env=env)
+      ['git', 'diff', '--no-ext-diff', '--stat', '--find-copies-harder'] + args,
+      env=env)
 
   if settings.GetIsGerrit():
     return GerritUpload(options, args, cl)

tests/git_cl_test.py

@@ -114,7 +114,8 @@ class TestGitCl(TestCase):
       ((['git', 'config', 'branch.master.rietveldpatchset'],), ''),
       ((['git', 'log', '--pretty=format:%s%n%n%b', 'master...'],), 'foo'),
       ((['git', 'config', 'user.email'],), 'me@example.com'),
-      ((['git', 'diff', '--no-ext-diff', '--stat', '-M', 'master...'],),
+      ((['git', 'diff', '--no-ext-diff', '--stat', '--find-copies-harder',
+         'master...'],),
        '+dat'),
       ((['git', 'log', '--pretty=format:%s\n\n%b', 'master..'],), 'desc\n'),
     ]
@@ -347,7 +348,8 @@ class TestGitCl(TestCase):
         ((['git', 'config', 'branch.master.rietveldpatchset'],), ''),
         ((['git', 'log', '--pretty=format:%s%n%n%b', 'master...'],), 'foo'),
         ((['git', 'config', 'user.email'],), 'me@example.com'),
-        ((['git', 'diff', '--no-ext-diff', '--stat', '-M', 'master...'],),
+        ((['git', 'diff', '--no-ext-diff', '--stat', '--find-copies-harder',
+           'master...'],),
          '+dat'),
         ]