Merge branch 'doc_rebase' into 'master'

separate documentation for rebase before merge

fixes https://dev.gitlab.org/gitlab/gitlabhq/issues/2108

See merge request !350

doc/workflow/README.md

@@ -3,6 +3,7 @@
 - [Feature branch workflow](workflow.md)
 - [Project Features](project_features.md)
 - [Authorization for merge requests](authorization_for_merge_requests.md)
+- [Rebase before merge](rebase_before_merge.md)
 - [Groups](groups.md)
 - [Share projects with other groups](share_projects_with_other_groups.md)
 - [Labels](labels.md)

doc/workflow/rebase_before_merge.md

+#Rebase before merge
+
+GitLab Enterprise Edition offers a way to rebase before merging a merge request. You can configure this per project basis by navigating to the project settings page and selecting `Merge Requests Rebase` checkbox.
+
+![Merge request settings](merge_request_settings.png)
+
+Before accepting a merge request, select `rebase before merge`.
+![Merge request widget](merge_request_widget.png)
+
+GitLab will attempt to cleanly rebase before merging branches. If clean rebase is not possible, regular merge will be performed.
+If clean rebase is possible and history of the traget branch will be altered with the the merge.
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