settings: Add argument to select rebase as merge strategy.

rhodecode/lib/vcs/backends/base.py

@@ -365,7 +365,8 b' class BaseRepository(object):'
         raise NotImplementedError
 
     def merge(self, target_ref, source_repo, source_ref, workspace_id,
-              user_name='', user_email='', message='', dry_run=False):
+              user_name='', user_email='', message='', dry_run=False,
+              use_rebase=False):
         """
         Merge the revisions specified in `source_ref` from `source_repo`
         onto the `target_ref` of this repository.
@@ -388,6 +389,8 b' class BaseRepository(object):'
         :param user_email: Merge commit `user_email`.
         :param message: Merge commit `message`.
         :param dry_run: If `True` the merge will not take place.
+        :param use_rebase: If `True` commits from the source will be rebased
+            on top of the target instead of being merged.
         """
         if dry_run:
             message = message or 'sample_message'
@@ -407,7 +410,8 b' class BaseRepository(object):'
         try:
             return self._merge_repo(
                 shadow_repository_path, target_ref, source_repo,
-                source_ref, message, user_name, user_email, dry_run=dry_run)
+                source_ref, message, user_name, user_email, dry_run=dry_run,
+                use_rebase=use_rebase)
         except RepositoryError:
             log.exception(
                 'Unexpected failure when running merge, dry-run=%s',

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

@@ -833,7 +833,8 b' class GitRepository(BaseRepository):'
 
     def _merge_repo(self, shadow_repository_path, target_ref,
                     source_repo, source_ref, merge_message,
-                    merger_name, merger_email, dry_run=False):
+                    merger_name, merger_email, dry_run=False,
+                    use_rebase=False):
         if target_ref.commit_id != self.branches[target_ref.name]:
             return MergeResponse(
                 False, False, None, MergeFailureReason.TARGET_IS_NOT_HEAD)

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

@@ -659,7 +659,8 b' class MercurialRepository(BaseRepository'
 
     def _merge_repo(self, shadow_repository_path, target_ref,
                     source_repo, source_ref, merge_message,
-                    merger_name, merger_email, dry_run=False):
+                    merger_name, merger_email, dry_run=False,
+                    use_rebase=False):
         if target_ref.commit_id not in self._heads():
             return MergeResponse(
                 False, False, None, MergeFailureReason.TARGET_IS_NOT_HEAD)