utils/version: add get_commit

Add a function to get the commit ID of the devlib repository (if running
from source, e.g. via "setup.py develop").

devlib/utils/version.py

@@ -0,0 +1,15 @@
+import os
+import sys
+from subprocess import Popen, PIPE
+
+def get_commit():
+    p = Popen(['git', 'rev-parse', 'HEAD'], cwd=os.path.dirname(__file__),
+              stdout=PIPE, stderr=PIPE)
+    std, _ = p.communicate()
+    p.wait()
+    if p.returncode:
+        return None
+    if sys.version_info[0] == 3:
+        return std[:8].decode(sys.stdout.encoding)
+    else:
+        return std[:8]