New functionality for cformat (#7893)

Fixing complexity

remove lambda

PR review fixes #1

Removing unneccesary string substitution

Handle -a and specified files

Complexity rewrite, use pathlib

1 files changed, 24 insertions, 2 deletions

diff --git a/docs/cli.md b/docs/cli.md
index 8ee8ab0e8..7c3effcc0 100644
--- a/docs/cli.md
+++ b/docs/cli.md
@@ -71,14 +71,36 @@ There are some limitations to the local CLI compared to the global CLI:
 
 ## `qmk cformat`
 
-This command formats C code using clang-format. Run it with no arguments to format all core code, or pass filenames on the command line to run it on specific files.
+This command formats C code using clang-format. 
 
-**Usage**:
+Run it with no arguments to format all core code that has been changed. Default checks `origin/master` with `git diff`, branch can be changed using `-b <branch_name>`
+
+Run it with `-a` to format all core code, or pass filenames on the command line to run it on specific files.
+
+**Usage for specified files**:
 
 ```
 qmk cformat [file1] [file2] [...] [fileN]
 ```
 
+**Usage for all core files**:
+
+```
+qmk cformat -a
+```
+
+**Usage for only changed files against origin/master**:
+
+```
+qmk cformat
+```
+
+**Usage for only changed files against branch_name**:
+
+```
+qmk cformat -b branch_name
+```
+
 ## `qmk compile`
 
 This command allows you to compile firmware from any directory. You can compile JSON exports from <https://config.qmk.fm>, compile keymaps in the repo, or compile the keyboard in the current working directory.