5X speed up of 'git cl format', which also speeds up 'git cl upload'

'git cl format' became very slow (7
seconds) after the Blink merge. 'git cl upload' is also slow when
the presubmit requires formatting checks.

This CL speeds up 'git cl format' by reducing the number of calls to
'git diff' and by removing the glob parameter. The glob
parameter adds a couple of seconds as it scans the entire
repository.

Before: 'git cl format' takes 7 seconds
After: 'git cl format' takes 1.25 seconds

BUG=577647

Review URL: https://codereview.chromium.org/1585923004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298323 0039d316-1c4b-4281-b951-d872f2087c98

git_cl.py

@@ -3472,7 +3472,7 @@ def CMDowners(parser, args):
       disable_color=options.no_color).run()
 
 
-def BuildGitDiffCmd(diff_type, upstream_commit, args, extensions):
+def BuildGitDiffCmd(diff_type, upstream_commit, args):
   """Generates a diff command."""
   # Generate diff for the current branch's changes.
   diff_cmd = ['diff', '--no-ext-diff', '--no-prefix', diff_type,
@@ -3480,17 +3480,16 @@ def BuildGitDiffCmd(diff_type, upstream_commit, args, extensions):
 
   if args:
     for arg in args:
-      if os.path.isdir(arg):
-        diff_cmd.extend(os.path.join(arg, '*' + ext) for ext in extensions)
-      elif os.path.isfile(arg):
+      if os.path.isdir(arg) or os.path.isfile(arg):
         diff_cmd.append(arg)
       else:
         DieWithError('Argument "%s" is not a file or a directory' % arg)
-  else:
-    diff_cmd.extend('*' + ext for ext in extensions)
 
   return diff_cmd
 
+def MatchingFileType(file_name, extensions):
+  """Returns true if the file name ends with one of the given extensions."""
+  return bool([ext for ext in extensions if file_name.lower().endswith(ext)])
 
 @subcommand.usage('[files or directories to diff]')
 def CMDformat(parser, args):
@@ -3527,15 +3526,13 @@ def CMDformat(parser, args):
     DieWithError('Could not find base commit for this branch. '
                  'Are you in detached state?')
 
-  if opts.full:
-    # Only list the names of modified files.
-    diff_type = '--name-only'
-  else:
-    # Only generate context-less patches.
-    diff_type = '-U0'
+  changed_files_cmd = BuildGitDiffCmd('--name-only', upstream_commit, args)
+  diff_output = RunGit(changed_files_cmd)
+  diff_files = diff_output.splitlines()
 
-  diff_cmd = BuildGitDiffCmd(diff_type, upstream_commit, args, CLANG_EXTS)
-  diff_output = RunGit(diff_cmd)
+  clang_diff_files = [x for x in diff_files if MatchingFileType(x, CLANG_EXTS)]
+  python_diff_files = [x for x in diff_files if MatchingFileType(x, ['.py'])]
+  dart_diff_files = [x for x in diff_files if MatchingFileType(x, ['.dart'])]
 
   top_dir = os.path.normpath(
       RunGit(["rev-parse", "--show-toplevel"]).rstrip('\n'))
@@ -3551,19 +3548,16 @@ def CMDformat(parser, args):
   return_value = 0
 
   if opts.full:
-    # diff_output is a list of files to send to clang-format.
-    files = diff_output.splitlines()
-    if files:
+    if clang_diff_files:
       cmd = [clang_format_tool]
       if not opts.dry_run and not opts.diff:
         cmd.append('-i')
-      stdout = RunCommand(cmd + files, cwd=top_dir)
+      stdout = RunCommand(cmd + clang_diff_files, cwd=top_dir)
       if opts.diff:
         sys.stdout.write(stdout)
   else:
     env = os.environ.copy()
     env['PATH'] = str(os.path.dirname(clang_format_tool))
-    # diff_output is a patch to send to clang-format-diff.py
     try:
       script = clang_format.FindClangFormatScriptInChromiumTree(
           'clang-format-diff.py')
@@ -3574,6 +3568,9 @@ def CMDformat(parser, args):
     if not opts.dry_run and not opts.diff:
       cmd.append('-i')
 
+    diff_cmd = BuildGitDiffCmd('-U0', upstream_commit, clang_diff_files)
+    diff_output = RunGit(diff_cmd)
+
     stdout = RunCommand(cmd, stdin=diff_output, cwd=top_dir, env=env)
     if opts.diff:
       sys.stdout.write(stdout)
@@ -3583,19 +3580,16 @@ def CMDformat(parser, args):
   # Similar code to above, but using yapf on .py files rather than clang-format
   # on C/C++ files
   if opts.python:
-    diff_cmd = BuildGitDiffCmd(diff_type, upstream_commit, args, ['.py'])
-    diff_output = RunGit(diff_cmd)
     yapf_tool = gclient_utils.FindExecutable('yapf')
     if yapf_tool is None:
       DieWithError('yapf not found in PATH')
 
     if opts.full:
-      files = diff_output.splitlines()
-      if files:
+      if python_diff_files:
         cmd = [yapf_tool]
         if not opts.dry_run and not opts.diff:
           cmd.append('-i')
-        stdout = RunCommand(cmd + files, cwd=top_dir)
+        stdout = RunCommand(cmd + python_diff_files, cwd=top_dir)
         if opts.diff:
           sys.stdout.write(stdout)
     else:
@@ -3603,18 +3597,14 @@ def CMDformat(parser, args):
       # https://github.com/google/yapf/issues/154
       DieWithError('--python currently only works with --full')
 
-  # Build a diff command that only operates on dart files. dart's formatter
-  # does not have the nice property of only operating on modified chunks, so
-  # hard code full.
-  dart_diff_cmd = BuildGitDiffCmd('--name-only', upstream_commit,
-                                  args, ['.dart'])
-  dart_diff_output = RunGit(dart_diff_cmd)
-  if dart_diff_output:
+  # Dart's formatter does not have the nice property of only operating on
+  # modified chunks, so hard code full.
+  if dart_diff_files:
     try:
       command = [dart_format.FindDartFmtToolInChromiumTree()]
       if not opts.dry_run and not opts.diff:
         command.append('-w')
-      command.extend(dart_diff_output.splitlines())
+      command.extend(dart_diff_files)
 
       stdout = RunCommand(command, cwd=top_dir, env=env)
       if opts.dry_run and stdout: