CLI: Add git and venv info to doctor's output (#13405)

Most of the checks are saved from zvecr's retired 'up/status'
subcommand PR.

lib/python/qmk/constants.py

@@ -6,6 +6,9 @@ from pathlib import Path
 # The root of the qmk_firmware tree.
 QMK_FIRMWARE = Path.cwd()
 
+# Upstream repo url
+QMK_FIRMWARE_UPSTREAM = 'qmk/qmk_firmware'
+
 # This is the number of directories under `qmk_firmware/keyboards` that will be traversed. This is currently a limitation of our make system.
 MAX_KEYBOARD_SUBFOLDERS = 5