Added diff option into git and hg changeset objects, representing git formated patch against parent1

rhodecode/lib/vcs/backends/git/changeset.py

@@ -194,6 +194,11 b' class GitChangeset(BaseChangeset):'
 
         return _prev(self, branch)
 
+    def diff(self, ignore_whitespace=True, context=3):
+        return ''.join(self.repository.get_diff(self, self.parents[0],
+                                    ignore_whitespace=ignore_whitespace,
+                                    context=context))
+
     def get_file_mode(self, path):
         """
         Returns stat mode of the file at the given ``path``.

rhodecode/lib/vcs/backends/git/repository.py

@@ -437,6 +437,12 b' class GitRepository(BaseRepository):'
         if ignore_whitespace:
             flags.append('-w')
 
+        if hasattr(rev1, 'raw_id'):
+            rev1 = getattr(rev1, 'raw_id')
+
+        if hasattr(rev2, 'raw_id'):
+            rev2 = getattr(rev2, 'raw_id')
+
         if rev1 == self.EMPTY_CHANGESET:
             rev2 = self.get_changeset(rev2).raw_id
             cmd = ' '.join(['show'] + flags + [rev2])

rhodecode/lib/vcs/backends/hg/changeset.py

@@ -136,6 +136,11 b' class MercurialChangeset(BaseChangeset):'
 
         return _prev(self, branch)
 
+    def diff(self, ignore_whitespace=True, context=3):
+        return ''.join(self._ctx.diff(git=True,
+                                      ignore_whitespace=ignore_whitespace,
+                                      context=context))
+
     def _fix_path(self, path):
         """
         Paths are stored without trailing slash so we need to get rid off it if