Add support for tab completion (#12411)

* Add support for tab completion

* make flake8 happy

* Add documentation

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/python/qmk/cli/cformat.py b/lib/python/qmk/cli/cformat.py
index c7e93b2ab..d0d3b3b0a 100644
--- a/lib/python/qmk/cli/cformat.py
+++ b/lib/python/qmk/cli/cformat.py
@@ -3,6 +3,7 @@
 import subprocess
 from shutil import which
 
+from argcomplete.completers import FilesCompleter
 from milc import cli
 
 from qmk.path import normpath
@@ -33,7 +34,7 @@ def cformat_run(files, all_files):
 
 @cli.argument('-a', '--all-files', arg_only=True, action='store_true', help='Format all core files.')
 @cli.argument('-b', '--base-branch', default='origin/master', help='Branch to compare to diffs to.')
-@cli.argument('files', nargs='*', arg_only=True, help='Filename(s) to format.')
+@cli.argument('files', nargs='*', arg_only=True, completer=FilesCompleter('.c'), help='Filename(s) to format.')
 @cli.subcommand("Format C code according to QMK's style.", hidden=False if cli.config.user.developer else True)
 def cformat(cli):
     """Format C code according to QMK's style.