Port tools/clang-format/git-clang-format to work Python beyond 2.7

[Andreas Bergmeier via cfe-commits]

Since Python3 may deliberately not be available on Linux Systems (to prevent people from writing non-futureproof code), git-clang-format should not only work with Python2.7. This patch adds support for Python3.

From 20175b753d8ef9f00f33fe04484dce1c0148ff7c Mon Sep 17 00:00:00 2001
From: Andreas Bergmeier <a.bergmeier at dsfishlabs.com>
Date: Wed, 17 Aug 2016 10:55:32 +0200
Subject: Use 2to3 on git-clang-format.


diff --git a/tools/clang-format/git-clang-format b/tools/clang-format/git-clang-format
index 0c45762..a2d7e7a 100755
--- a/tools/clang-format/git-clang-format
+++ b/tools/clang-format/git-clang-format
@@ -20,9 +20,11 @@ clang-format on the changes in current files or a specific commit.
 For further details, run:
 git clang-format -h

-Requires Python 2.7
+Requires a minimum of Python 2.7
 """

+from __future__ import print_function
+
 import argparse
 import collections
 import contextlib
@@ -128,15 +130,15 @@ def main():
   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('   ', 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('   ', 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.
@@ -146,20 +148,20 @@ def main():
                                                binary=opts.binary,
                                                style=opts.style)
   if opts.verbose >= 1:
-    print 'old tree:', old_tree
-    print 'new tree:', new_tree
+    print('old tree:', old_tree)
+    print('new tree:', 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('   ', filename)


 def load_git_config(non_string_options=None):
@@ -298,7 +300,7 @@ def filter_by_extension(dictionary, allowed_extensions):
   `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]
@@ -323,7 +325,7 @@ def run_clang_format_and_save_to_tree(changed_lines, binary='clang-format',

   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.items():
       mode = oct(os.stat(filename).st_mode)
       blob_id = clang_format_to_blob(filename, line_ranges, binary=binary,
                                      style=style)
@@ -431,10 +433,10 @@ def apply_changes(old_tree, new_tree, force=False, patch_mode=False):
   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
@@ -464,20 +466,20 @@ def run(*args, **kwargs):
   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)


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