Initial abstraction for VCS

The code is not yet used yet, it's just a draft of how the class might
look like.

See issue #511 and #126
Signed-off-by: Michal Čihař <michal@cihar.com>

weblate/trans/tests/test_vcs.py

+# -*- coding: utf-8 -*-
+#
+# Copyright © 2012 - 2014 Michal Čihař <michal@cihar.com>
+#
+# This file is part of Weblate <http://weblate.org/>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+from weblate.trans.tests.test_models import RepoTestCase
+from weblate.trans.vcs import GitRepository
+
+import tempfile
+import shutil
+
+
+class VCSGitTest(RepoTestCase):
+    def test_clone(self):
+        tempdir = tempfile.mkdtemp()
+        try:
+            GitRepository.clone(self.repo_path, tempdir)
+        finally:
+            shutil.rmtree(tempdir)
+
+    def test_revision(self):
+        tempdir = tempfile.mkdtemp()
+        try:
+            repo = GitRepository.clone(self.repo_path, tempdir)
+            self.assertEquals(
+                repo.last_revision,
+                repo.last_remote_revision
+            )
+        finally:
+            shutil.rmtree(tempdir)

weblate/trans/vcs.py

+# -*- coding: utf-8 -*-
+#
+# Copyright © 2012 - 2014 Michal Čihař <michal@cihar.com>
+#
+# This file is part of Weblate <http://weblate.org/>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+"""
+Minimal distributed version control system abstraction for Weblate needs.
+"""
+import subprocess
+
+
+class RepositoryException(Exception):
+    """
+    Error while working with a repository.
+    """
+
+
+class Repository(object):
+    """
+    Basic repository object.
+    """
+    _last_revision = None
+    _last_remote_revision = None
+    _cmd = 'false'
+    _cmd_last_revision = []
+    _cmd_last_remote_revision = []
+    _cmd_clone = 'clone'
+
+    def __init__(self, path):
+        self.path = path
+
+    @classmethod
+    def _popen(cls, args, cwd=None):
+        args.insert(0, cls._cmd)
+        process = subprocess.Popen(
+            args,
+            cwd=cwd,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+        )
+        output, output_err = process.communicate()
+        retcode = process.poll()
+        if retcode:
+            raise RepositoryException(output_err)
+        return output
+
+    def _execute(self, args):
+        return self._popen(args, self.path)
+
+    @property
+    def last_revision(self):
+        if self._last_revision is None:
+            self._last_revision = self._execute(
+                self._cmd_last_revision
+            )
+        return self._last_revision
+
+    @property
+    def last_remote_revision(self):
+        if self._last_remote_revision is None:
+            self._last_remote_revision = self._execute(
+                self._cmd_last_remote_revision
+            )
+        return self._last_remote_revision
+
+    @classmethod
+    def clone(cls, source, target):
+        """
+        Clones repository and returns Repository object for cloned
+        repository.
+        """
+        cls._popen([cls._cmd_clone, source, target])
+        return cls(target)
+
+
+class GitRepository(Repository):
+    """
+    Repository implementation for Git.
+    """
+    _cmd = 'git'
+    _cmd_last_revision = [
+        'log', '-n', '1', '--format=format:%H', '@'
+    ]
+    _cmd_last_remote_revision = [
+        'log', '-n', '1', '--format=format:%H', '@{upstream}'
+    ]