[git-clang-format] Add --diffstat parameter

[roligugus]

Summary

[git-clang-format][PR46815] Add diffstat functionality

Adding a --diffstat parameter to git-clang-format that essentially uses git diff --stat, i.e. lists the files needing
formatting. This is useful for CI integration or manual usage where one wants to list the files not properly formatted.

I use it for the Suricata project's github action (CI) integration that verifies proper formatting of a pull request
according to project guidelines where it's very helpful to say which files are not properly formatted. I find the list
of files much more useful than e.g. showing the diff in this case using git-clang-format --diff.

An alternative would be to take an additional parameter to diff, e.g. git-clang-format --diff --stat

The goal is not to provide the whole git diff --stat=... parameter functionality, just plain git diff --stat.

[roligugus]

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

102

As mentioned in the description, an alternative would be to add a --stat parameter and hand that to print_diff(). E.g. user would call it then with git-clang-format --diff --stat.

Would result in less code duplication of print_diff() vs print_diffstat().

[aheejin]

This looks fine to me, but I haven't worked on this part of code myself, so probably others who have can provide better review.

[JakeMerdichAMD]

Reviving this since it looks perfectly fine to me (from my limited commit history in git-clang-format :P), is useful, and there's no good reason for it to be stalled.

I'll wait a day or two to see if there's any objections, then accept it.

[roligugus]

@JakeMerdichAMD, @MyDeveloperDay
Sorry to bother with a re-review. Did not know how to ask this.

Jake accepted this patch last August and it has been sitting in "ready to land" since then. I was assuming that it'll automatically make it into the main line after the acceptance. My bad, I should have read the policy and practices better.

Do you mind re-accepting and then committing this? I don't have any commit rights.

Sorry, I should have followed up way earlier. I was finally getting around to this and wanted to take our local patch out and was assuming this was in the latest clang, but it isn't.

[MyDeveloperDay]

@roligugus I can land this for you, please rebase the review then please add your name and email here so we can ensure you get the credit.

https://llvm.org/docs/DeveloperPolicy.html#commit-messages

[roligugus]

[git-clang-format] Rebase D84375 on latest main

[roligugus]

@MyDeveloperDay Thanks for the follow-up! I've rebased on latest main.

Out of curiosity, as I am trying to wrap my head around the llvm workflow: Could I arc land ... myself once you sign off with "ready to land" even if I don't have llvm commit rights? If so, please let me know and I'll do that.

Otherwise, I've set the author on my commit, but if you need to set it: git commit --amend --author="Roland Fischer <[e-mail]>"

Thanks a lot!

[MyDeveloperDay]

In D84375#3065785, @roligugus wrote:

@MyDeveloperDay Thanks for the follow-up! I've rebased on latest main.

Out of curiosity, as I am trying to wrap my head around the llvm workflow: Could I arc land ... myself once you sign off with "ready to land" even if I don't have llvm commit rights? If so, please let me know and I'll do that.

Otherwise, I've set the author on my commit, but if you need to set it: git commit --amend --author="Roland Fischer <[e-mail]>"

Thanks a lot!

I personally don't use arc so I can't answer that, you DO need commit rights though, and you are free to apply for those. (normally I think you need to do some small issues first), but its worth applying if you plan to continue to contribute

I can land this for you for now.

[MyDeveloperDay]

I just tested this an it seems to work

$ git clang-format --diffstat
 clang/lib/Format/Format.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

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

def main():
   p.add_argument('--binary',
                  default=config.get('clangformat.binary', 'clang-format'),
                  help='path to clang-format'),
   p.add_argument('--commit',
                  default=config.get('clangformat.commit', 'HEAD'),
                  help='default commit to use if none is specified'),
   p.add_argument('--diff', action='store_true',
                  help='print a diff instead of applying the changes')
+  p.add_argument('--diffstat', action='store_true',
+                 help='print a diffstat instead of applying the changes')
   p.add_argument('--extensions',
                  default=config.get('clangformat.extensions',
                                     default_extensions),
                  help=('comma-separated list of file extensions to format, '
                        'excluding the period and case-insensitive')),
   p.add_argument('-f', '--force', action='store_true',
                  help='allow changes to unstaged files')
   p.add_argument('-p', '--patch', action='store_true',
def main():
   if opts.verbose >= 1:
     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')
   elif opts.diff:
     print_diff(old_tree, new_tree)
+  elif opts.diffstat:
+    print_diffstat(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:')
       for filename in changed_files:
         print('    %s' % filename)
 
def print_diff(old_tree, new_tree):
   # like color and pagination.
   #
   # We also only print modified files since `new_tree` only contains the files
   # that were modified, so unmodified files would show as deleted without the
   # filter.
   subprocess.check_call(['git', 'diff', '--diff-filter=M', old_tree, new_tree,
                          '--'])
 
+def print_diffstat(old_tree, new_tree):
+  """Print the diffstat between the two trees to stdout."""
+  # We use the porcelain 'diff' and not plumbing 'diff-tree' because the output
+  # is expected to be viewed by the user, and only the former does nice things
+  # like color and pagination.
+  #
+  # We also only print modified files since `new_tree` only contains the files
+  # that were modified, so unmodified files would show as deleted without the
+  # filter.
+  subprocess.check_call(['git', 'diff', '--diff-filter=M', '--stat', old_tree, new_tree,
+                         '--'])
 
 def apply_changes(old_tree, new_tree, force=False, patch_mode=False):
   """Apply the changes in `new_tree` to the working directory.
 
   Bails if there are local changes in those files and not `force`.  If
   `patch_mode`, runs `git checkout --patch` to select hunks interactively."""
   changed_files = run('git', 'diff-tree', '--diff-filter=M', '-r', '-z',
                       '--name-only', old_tree,