handle the case where qmk_firmware exists but isn't a clone

qmk_cli/subcommands/setup.py

@@ -83,6 +83,15 @@ def setup(cli):
     if is_qmk_firmware(cli.args.home):
         cli.log.info('Found qmk_firmware at %s.', str(cli.args.home))
 
+    elif qmk_firmware.exists():
+        path_str = str(qmk_firmware)
+
+        if qmk_firmware.name != 'qmk_firmware':
+            cli.log.warning('Warning: %s does not end in "qmk_firmware". Did you mean to use "--home %s/qmk_firmware"?' % (path_str, path_str))
+
+        cli.log.error("Path '%s' exists but is not a qmk_firmware clone!", path_str)
+        exit(1)
+
     else:
         cli.log.error('Could not find qmk_firmware!')
         if yesno(clone_prompt):