[git-clang-format] Do not apply clang-format to symlinks

[pirama]

Summary

This fixes PR46992.

Git stores symlinks as text files and we should not format them even if
they have one of the requested extensions.

(Move the call to cd_to_toplevel() up a few lines so we can also print
the skipped symlinks during verbose output.)

[pirama]

Leave two empty lines after filter_symlinks.

[HazardyKnusperkeks]

I have not a great knowledge about python, but it looks okay.

[curdeius]

clang/tools/clang-format/git-clang-format

345

Is this print supposed to stay or is it a remnant of print-debugging?

[pirama]

Remove debug print().

[pirama]

clang/tools/clang-format/git-clang-format

345

Oops, can't believe it slipped through. Sorry about that.

[curdeius]

LGTM but let's wait a day or two before landing, so that others can chime in.
Btw, do you have commit rights? If no, please provide "Name <email>" for commit attribution.

clang/tools/clang-format/git-clang-format

345

No worries, the review serves its purpose!

[pirama]

In D101878#2740133, @curdeius wrote:

LGTM but let's wait a day or two before landing, so that others can chime in.
Btw, do you have commit rights? If no, please provide "Name <email>" for commit attribution.

Yes, I do have commit rights. Let's wait for comments and I'll submit it on Monday.

[curdeius]

Oh, I forgot, please add a release note.

[pirama]

Add release note

clang/tools/clang-format/git-clang-format

if not opts.diff:
       die('--diff is required when two commits are given')
   else:
     if len(commits) > 2:
       die('at most two commits allowed; %d given' % len(commits))
   changed_lines = compute_diff_and_extract_lines(commits, files)
   if opts.verbose >= 1:
     ignored_files = set(changed_lines)
   filter_by_extension(changed_lines, opts.extensions.lower().split(','))
+  # The computed diff outputs absolute paths, so we must cd before accessing
+  # those files.
+  cd_to_toplevel()
+  filter_symlinks(changed_lines)
   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 or symlink):')
       for filename in ignored_files:
         print('    %s' % filename)
     if changed_lines:
       print('Running clang-format on the following files:')
       for filename in changed_lines:
         print('    %s' % filename)
   if not changed_lines:
     if opts.verbose >= 0:
       print('no modified files to format')
     return
-  # The computed diff outputs absolute paths, so we must cd before accessing
-  # those files.
-  cd_to_toplevel()
   if len(commits) > 1:
     old_tree = commits[1]
     new_tree = run_clang_format_and_save_to_tree(changed_lines,
                                                  revision=commits[1],
                                                  binary=opts.binary,
                                                  style=opts.style)
   else:
     old_tree = create_tree_from_workdir(changed_lines)
def filter_by_extension(dictionary, allowed_extensions):
   for filename in list(dictionary.keys()):
     base_ext = filename.rsplit('.', 1)
     if len(base_ext) == 1 and '' in allowed_extensions:
         continue
     if len(base_ext) == 1 or base_ext[1].lower() not in allowed_extensions:
       del dictionary[filename]
 
 
+def filter_symlinks(dictionary):
+  """Delete every key in `dictionary` that is a symlink."""
+  for filename in list(dictionary.keys()):
+    if os.path.islink(filename):
+      del dictionary[filename]
+
+
 def cd_to_toplevel():
   """Change to the top level of the git repository."""
   toplevel = run('git', 'rev-parse', '--show-toplevel')
   os.chdir(toplevel)
 
 
 def create_tree_from_workdir(filenames):
   """Create a new git tree with the given files from the working directory.