implement borgmajor/minor/patch placeholders, fixes #1694

borg/__init__.py

@@ -1,11 +1,6 @@
-import re
+from distutils.version import LooseVersion
 
 from ._version import version as __version__
 
-version_re = r'(\d+)\.(\d+)\.(\d+)'
 
-m = re.match(version_re, __version__)
-if m:
-    __version_tuple__ = tuple(map(int, m.groups()))
-else:
-    raise RuntimeError("Can't parse __version__: %r" % __version__)
+__version_tuple__ = tuple(LooseVersion(__version__).version[:3])