Add is_supported method to VCS backend

Signed-off-by: Michal Čihař <michal@cihar.com>

requirements-optional.txt

@@ -2,4 +2,4 @@
 PyICU
 pyLibravatar
 babel
-Mercurial
+Mercurial>=2.8

weblate/trans/tests/test_vcs.py

@@ -117,6 +117,9 @@ class VCSGitTest(RepoTestCase):
         self.assertFalse(self.repo.needs_merge(self._branch))
         self.assertFalse(self.repo.needs_push(self._branch))
 
+    def test_is_supported(self):
+        self.assertTrue(self._class.is_supported())
+
     def test_get_version(self):
         self.assertTrue(self._class.get_version() != '')
 

weblate/trans/vcs.py

@@ -26,6 +26,7 @@ import email.utils
 import re
 import ConfigParser
 import hashlib
+from distutils.version import LooseVersion
 from dateutil import parser
 from weblate.trans.util import get_clean_env
 
@@ -215,6 +216,17 @@ class Repository(object):
         """
         raise NotImplementedError()
 
+    @classmethod
+    def is_supported(cls):
+        """
+        Checks whether this VCS backend is supported.
+        """
+        try:
+            cls.get_version()
+            return True
+        except OSError:
+            return False
+
     @classmethod
     def get_version(cls):
         """
@@ -433,6 +445,17 @@ class GitRepository(Repository):
         """
         return self._log_revisions('origin/{0}..'.format(branch)) != ''
 
+    @classmethod
+    def is_supported(cls):
+        """
+        Checks whether this VCS backend is supported.
+        """
+        try:
+            version = cls.get_version()
+            return LooseVersion(version) >= '1.6'
+        except OSError:
+            return False
+
     @classmethod
     def get_version(cls):
         """
@@ -735,6 +758,17 @@ class HgRepository(Repository):
         """
         return self.execute(['log', '-r', 'not public()']) != ''
 
+    @classmethod
+    def is_supported(cls):
+        """
+        Checks whether this VCS backend is supported.
+        """
+        try:
+            version = cls.get_version()
+            return LooseVersion(version) >= '2.8'
+        except OSError:
+            return False
+
     @classmethod
     def get_version(cls):
         """