Add back support for git mv files.

It was added in r80045 but was overwriten in r82495 when I synced upload.py to
r705 since upstreaming that part staled.

TBR=dpranke
TEST="git mv foo bar; git commit -a; git cl upload" shows 2 files, one A+, one D.
BUG=none

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@84264 0039d316-1c4b-4281-b951-d872f2087c98

third_party/upload.py

@@ -1230,8 +1230,19 @@ class GitVCS(VersionControlSystem):
     # git config key "diff.external" is used).
     env = os.environ.copy()
     if 'GIT_EXTERNAL_DIFF' in env: del env['GIT_EXTERNAL_DIFF']
-    return RunShell(["git", "diff", "--no-ext-diff", "--full-index", "-M"]
+    # -M/-C will not print the diff for the deleted file when a file is renamed.
-                    + extra_args, env=env)
+    # This is confusing because the original file will not be shown on the
+    # review when a file is renamed. So first get the diff of all deleted files,
+    # then the diff of everything except deleted files with rename and copy
+    # support enabled.
+    cmd = ["git", "diff", "--no-ext-diff", "--full-index"]
+    diff = RunShell(cmd + ["--diff-filter=D"] + extra_args, env=env,
+        silent_ok=True)
+    diff += RunShell(cmd + ["-C", "--diff-filter=ACMRT"] + extra_args, env=env,
+        silent_ok=True)
+    if not diff:
+      ErrorExit("No output from %s" % (cmd + extra_args))
+    return diff
 
   def GetUnknownFiles(self):
     status = RunShell(["git", "ls-files", "--exclude-standard", "--others"],