Fix "No C files in filelist: None" (#15560)

* Fix "No C files in filelist: None"

* Align other commands

* force absolute paths

lib/python/qmk/cli/format/c.py

@@ -1,6 +1,5 @@
 """Format C code according to QMK's style.
 """
-from os import path
 from shutil import which
 from subprocess import CalledProcessError, DEVNULL, Popen, PIPE
 
@@ -15,6 +14,12 @@ core_dirs = ('drivers', 'quantum', 'tests', 'tmk_core', 'platforms')
 ignored = ('tmk_core/protocol/usb_hid', 'platforms/chibios/boards')
 
 
+def is_relative_to(file, other):
+    """Provide similar behavior to PurePath.is_relative_to in Python > 3.9
+    """
+    return str(normpath(file).resolve()).startswith(str(normpath(other).resolve()))
+
+
 def find_clang_format():
     """Returns the path to clang-format.
     """
@@ -68,18 +73,19 @@ def cformat_run(files):
 def filter_files(files, core_only=False):
     """Yield only files to be formatted and skip the rest
     """
+    files = list(map(normpath, filter(None, files)))
     if core_only:
         # Filter non-core files
         for index, file in enumerate(files):
             # The following statement checks each file to see if the file path is
             # - in the core directories
             # - not in the ignored directories
-            if not any(str(file).startswith(i) for i in core_dirs) or any(str(file).startswith(i) for i in ignored):
-                files[index] = None
+            if not any(is_relative_to(file, i) for i in core_dirs) or any(is_relative_to(file, i) for i in ignored):
+                del files[index]
                 cli.log.debug("Skipping non-core file %s, as '--core-only' is used.", file)
 
     for file in files:
-        if file and file.name.split('.')[-1] in c_file_suffixes:
+        if file.suffix[1:] in c_file_suffixes:
             yield file
         else:
             cli.log.debug('Skipping file %s', file)
@@ -118,12 +124,8 @@ def format_c(cli):
             print(git_diff.stderr)
             return git_diff.returncode
 
-        files = []
-
-        for file in git_diff.stdout.strip().split('\n'):
-            if not any([file.startswith(ignore) for ignore in ignored]):
-                if path.exists(file) and file.split('.')[-1] in c_file_suffixes:
-                    files.append(file)
+        changed_files = git_diff.stdout.strip().split('\n')
+        files = list(filter_files(changed_files, True))
 
     # Sanity check
     if not files:

lib/python/qmk/cli/format/python.py

@@ -25,8 +25,9 @@ def yapf_run(files):
 def filter_files(files):
     """Yield only files to be formatted and skip the rest
     """
+    files = list(map(normpath, filter(None, files)))
     for file in files:
-        if file and normpath(file).name.split('.')[-1] in py_file_suffixes:
+        if file.suffix[1:] in py_file_suffixes:
             yield file
         else:
             cli.log.debug('Skipping file %s', file)