Use --internal-diff on svn 1.7+ to slightly reduce disk thrashing.

This just saves the need to create and remove an empty directory on every call to GenerateDiff.

Review URL: https://chromiumcodereview.appspot.com/14064017

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@195328 0039d316-1c4b-4281-b951-d872f2087c98

scm.py

@@ -781,21 +781,34 @@ class SVN(object):
     The diff will always use relative paths.
     """
     assert isinstance(filenames, (list, tuple))
+    # If the user specified a custom diff command in their svn config file,
+    # then it'll be used when we do svn diff, which we don't want to happen
+    # since we want the unified diff.
+    if SVN.AssertVersion("1.7")[0]:
+      # On svn >= 1.7, the "--internal-diff" flag will solve this.
+      return SVN._GenerateDiffInternal(filenames, cwd, full_move, revision,
+                                       ["diff", "--internal-diff"])
+    else:
+      # On svn < 1.7, the "--internal-diff" flag doesn't exist.  Using
+      # --diff-cmd=diff doesn't always work, since e.g. Windows cmd users may
+      # not have a "diff" executable in their path at all.  So we use an empty
+      # temporary directory as the config directory, which bypasses any user
+      # settings for the diff-cmd.
+      bogus_dir = tempfile.mkdtemp()
+      try:
+        return SVN._GenerateDiffInternal(filenames, cwd, full_move, revision,
+                                         ["diff", "--config_dir", bogus_dir])
+      finally:
+        gclient_utils.RemoveDirectory(bogus_dir)
+
+  @staticmethod
+  def _GenerateDiffInternal(filenames, cwd, full_move, revision, diff_command):
     root = os.path.normcase(os.path.join(cwd, ''))
     def RelativePath(path, root):
       """We must use relative paths."""
       if os.path.normcase(path).startswith(root):
         return path[len(root):]
       return path
-    # If the user specified a custom diff command in their svn config file,
-    # then it'll be used when we do svn diff, which we don't want to happen
-    # since we want the unified diff.  Using --diff-cmd=diff doesn't always
-    # work, since e.g. Windows cmd users may not have a "diff" executable in
-    # their path at all.  So we use an empty temporary directory as the config
-    # directory, which gets around these problems.
-    bogus_dir = tempfile.mkdtemp()
-    command = ['diff', '--config-dir', bogus_dir]
-    try:
     # Cleanup filenames
     filenames = [RelativePath(f, root) for f in filenames]
     # Get information about the modified items (files and directories)
@@ -832,14 +845,13 @@ class SVN(object):
             # revision the file was deleted.
             srcinfo = {'Revision': rev}
           if (srcinfo.get('Revision') != rev and
-                SVN.Capture(command + ['-r', '%d:head' % rev, srcurl], cwd)):
+              SVN.Capture(diff_command + ['-r', '%d:head' % rev, srcurl], cwd)):
             metaheaders.append("#$ svn cp -r %d %s %s "
                                "### WARNING: note non-trunk copy\n" %
                                (rev, src, filename))
           else:
             metaheaders.append("#$ cp %s %s\n" % (src,
                                                   filename))
-
       if metaheaders:
         diffs.append("### BEGIN SVN COPY METADATA\n")
         diffs.extend(metaheaders)
@@ -847,7 +859,7 @@ class SVN(object):
     # Now ready to do the actual diff.
     for filename in sorted(data):
       diffs.append(SVN._DiffItemInternal(
-            filename, cwd, data[filename], command, full_move, revision))
+          filename, cwd, data[filename], diff_command, full_move, revision))
     # Use StringIO since it can be messy when diffing a directory move with
     # full_move=True.
     buf = cStringIO.StringIO()
@@ -856,8 +868,6 @@ class SVN(object):
     result = buf.getvalue()
     buf.close()
     return result
-    finally:
-      gclient_utils.RemoveDirectory(bogus_dir)
 
   @staticmethod
   def _DiffItemInternal(filename, cwd, info, diff_command, full_move, revision):