Begin making git-clang-format python3 compatible.

This patch fixes most of the python3 incompatabilities
within git-clang-format while keeping the script python2 compatible.
There is still one remaining incompatability that prevents using Python3
which is the `str` vs `byte` type change. I plan to put those fixes
up for review separately.

This patch contains fixes for the following incompatabilities:

1) Use the new style Python3 `print` function. This requires importing
   __future__.print_function.

2) Fix incompatability between the Python3 octal prefix and the
   octal prefix Git uses.

3) Replace use of dict.iteritems() with dict.viewitems() because iteritems()
   has been removed in Python3. viewitems() reviews python 2.7 but that is
   also what the script is documented as requiring.

git-svn-id: svn://svn.chromium.org/llvm-project/cfe/trunk/tools/clang-format@300891 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
diff --git a/git-clang-format b/git-clang-format
index 74fd451..12146bf 100755
--- a/git-clang-format
+++ b/git-clang-format
@@ -23,6 +23,7 @@
 Requires Python 2.7                                                              
 """               
 
+from __future__ import print_function
 import argparse
 import collections
 import contextlib
@@ -138,15 +139,15 @@
   if opts.verbose >= 1:
     ignored_files.difference_update(changed_lines)
     if ignored_files:
-      print 'Ignoring changes in the following files (wrong extension):'
+      print('Ignoring changes in the following files (wrong extension):')
       for filename in ignored_files:
-        print '   ', filename
+        print('    %s' % filename)
     if changed_lines:
-      print 'Running clang-format on the following files:'
+      print('Running clang-format on the following files:')
       for filename in changed_lines:
-        print '   ', filename
+        print('    %s' % filename)
   if not changed_lines:
-    print 'no modified files to format'
+    print('no modified files to format')
     return
   # The computed diff outputs absolute paths, so we must cd before accessing
   # those files.
@@ -163,20 +164,20 @@
                                                  binary=opts.binary,
                                                  style=opts.style)
   if opts.verbose >= 1:
-    print 'old tree:', old_tree
-    print 'new tree:', new_tree
+    print('old tree: %s' % old_tree)
+    print('new tree: %s' % new_tree)
   if old_tree == new_tree:
     if opts.verbose >= 0:
-      print 'clang-format did not modify any files'
+      print('clang-format did not modify any files')
   elif opts.diff:
     print_diff(old_tree, new_tree)
   else:
     changed_files = apply_changes(old_tree, new_tree, force=opts.force,
                                   patch_mode=opts.patch)
     if (opts.verbose >= 0 and not opts.patch) or opts.verbose >= 1:
-      print 'changed files:'
+      print('changed files:')
       for filename in changed_files:
-        print '   ', filename
+        print('    %s' % filename)
 
 
 def load_git_config(non_string_options=None):
@@ -320,7 +321,7 @@
   `allowed_extensions` must be a collection of lowercase file extensions,
   excluding the period."""
   allowed_extensions = frozenset(allowed_extensions)
-  for filename in dictionary.keys():
+  for filename in list(dictionary.keys()):
     base_ext = filename.rsplit('.', 1)
     if len(base_ext) == 1 or base_ext[1].lower() not in allowed_extensions:
       del dictionary[filename]
@@ -345,7 +346,7 @@
 
   Returns the object ID (SHA-1) of the created tree."""
   def index_info_generator():
-    for filename, line_ranges in changed_lines.iteritems():
+    for filename, line_ranges in changed_lines.viewitems():
       if revision:
         git_metadata_cmd = ['git', 'ls-tree',
                             '%s:%s' % (revision, os.path.dirname(filename)),
@@ -356,6 +357,9 @@
         mode = oct(int(stdout.split()[0], 8))
       else:
         mode = oct(os.stat(filename).st_mode)
+      # Adjust python3 octal format so that it matches what git expects
+      if mode.startswith('0o'):
+          mode = '0' + mode[2:]
       blob_id = clang_format_to_blob(filename, line_ranges,
                                      revision=revision,
                                      binary=binary,
@@ -488,10 +492,10 @@
   if not force:
     unstaged_files = run('git', 'diff-files', '--name-status', *changed_files)
     if unstaged_files:
-      print >>sys.stderr, ('The following files would be modified but '
-                           'have unstaged changes:')
-      print >>sys.stderr, unstaged_files
-      print >>sys.stderr, 'Please commit, stage, or stash them first.'
+      print('The following files would be modified but '
+                'have unstaged changes:', file=sys.stderr)
+      print(unstaged_files, file=sys.stderr)
+      print('Please commit, stage, or stash them first.', file=sys.stderr)
       sys.exit(2)
   if patch_mode:
     # In patch mode, we could just as well create an index from the new tree
@@ -521,20 +525,20 @@
   if p.returncode == 0:
     if stderr:
       if verbose:
-        print >>sys.stderr, '`%s` printed to stderr:' % ' '.join(args)
-      print >>sys.stderr, stderr.rstrip()
+        print('`%s` printed to stderr:' % ' '.join(args), file=sys.stderr)
+      print(stderr.rstrip(), file=sys.stderr)
     if strip:
       stdout = stdout.rstrip('\r\n')
     return stdout
   if verbose:
-    print >>sys.stderr, '`%s` returned %s' % (' '.join(args), p.returncode)
+    print('`%s` returned %s' % (' '.join(args), p.returncode), file=sys.stderr)
   if stderr:
-    print >>sys.stderr, stderr.rstrip()
+    print(stderr.rstrip(), file=sys.stderr)
   sys.exit(2)
 
 
 def die(message):
-  print >>sys.stderr, 'error:', message
+  print('error:', message, file=sys.stderr)
   sys.exit(2)