Respect version hyphenation

The last change regarding version parsing lost handling of version
hyphenation, this restores that.  In otherwords,
1.1.1-otherstuff is parsed as (1,1,1) instead of (1,1,0)

Change-Id: I3753944e92095606653835ed2bd090b9301c7194

git_command.py

@@ -88,7 +88,7 @@ class _GitCall(object):
     if _git_version is None:
       ver_str = git.version().decode('utf-8')
       if ver_str.startswith('git version '):
-        num_ver_str = ver_str[len('git version '):].strip()
+        num_ver_str = ver_str[len('git version '):].strip().split('-')[0]
         to_tuple = []
         for num_str in num_ver_str.split('.')[:3]:
           if num_str.isdigit():