Use pathlib everywhere we can (#7872)

* Use pathlib everywhere we can

* Update lib/python/qmk/path.py

Co-Authored-By: Erovia <Erovia@users.noreply.github.com>

* Update lib/python/qmk/path.py

Co-Authored-By: Erovia <Erovia@users.noreply.github.com>

* Improvements based on @erovia's feedback

* rework qmk compile and qmk flash to use pathlib

* style

* Remove the subcommand_name argument from find_keyboard_keymap()

Co-authored-by: Erovia <Erovia@users.noreply.github.com>

lib/python/qmk/path.py

@@ -8,6 +8,35 @@ from qmk.constants import QMK_FIRMWARE, MAX_KEYBOARD_SUBFOLDERS
 from qmk.errors import NoSuchKeyboardError
 
 
+def is_keymap_dir(keymap_path):
+    """Returns True if `keymap_path` is a valid keymap directory.
+    """
+    keymap_path = Path(keymap_path)
+    keymap_c = keymap_path / 'keymap.c'
+    keymap_json = keymap_path / 'keymap.json'
+
+    return any((keymap_c.exists(), keymap_json.exists()))
+
+
+def is_keyboard(keyboard_name):
+    """Returns True if `keyboard_name` is a keyboard we can compile.
+    """
+    keyboard_path = QMK_FIRMWARE / 'keyboards' / keyboard_name
+    rules_mk = keyboard_path / 'rules.mk'
+    return rules_mk.exists()
+
+
+def under_qmk_firmware():
+    """Returns a Path object representing the relative path under qmk_firmware, or None.
+    """
+    cwd = Path(os.environ['ORIG_CWD'])
+
+    try:
+        return cwd.relative_to(QMK_FIRMWARE)
+    except ValueError:
+        return None
+
+
 def keymap(keyboard):
     """Locate the correct directory for storing a keymap.
 
@@ -39,5 +68,3 @@ def normpath(path):
         return Path(path)
 
     return Path(os.environ['ORIG_CWD']) / path
-
-    return os.path.normpath(os.path.join(os.environ['ORIG_CWD'], path))