probe: add basic os family detection

Add a basic OS family enumeration: OSFamily.

Add utility function that probes for an installed Linux or Windows
system, returns the corresponding enum value, OSFamily.UNKNOWN
otherwise.

src/utils/probe.py

@@ -10,10 +10,13 @@ import os
 import subprocess
 import platform
 
+from enum import Enum
 from subprocess import PIPE
 
 from src.utils.fs import find_mountpoint
 
+OSFamily = Enum('OSFamily', ['LINUX', 'WINDOWS', 'UNKNOWN'])
+
 def getlinuxversion(osrelease):
     """
     Parses a os-release file to fetch 'PRETTY_NAME' key.
@@ -115,6 +118,19 @@ def cache_probe():
     stdout = proc_blkid.stdout.decode().strip()
     return stdout
 
+
+def get_os_family(mountpoint):
+    winreghives = f'{mountpoint}/Windows/System32/'
+    osrelease = f'{mountpoint}/etc/os-release'
+
+    if os.path.exists(osrelease):
+        return OSFamily.LINUX
+    elif os.path.exists(winreghives):
+        return OSFamily.WINDOWS
+    else:
+        return OSFamily.UNKNOWN
+
+
 def os_probe(mountpoint):
     """
     Probes mountpoint for typical OS dependant files.