Merge "Added doc for git-rebase workflow."

doc/contributor-guide/source/additional-git-workflow.rst

@@ -13,3 +13,4 @@ while contributing to OpenStack documentation.
 
    additional-git-workflow/cherry-pick.rst
    additional-git-workflow/backport.rst
+   additional-git-workflow/rebase.rst

doc/contributor-guide/source/additional-git-workflow/rebase.rst

@@ -0,0 +1,81 @@
+.. _git-rebase:
+
+Resolving merge conflicts
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If the change that you submitted has a merge conflict,
+you need to manually resolve it using :command:`git rebase`.
+
+Rebasing is used to integrate changes from one branch into another to
+resolve conflicts when multiple commits happen on the same file.
+
+.. warning::
+
+   Never do a rebase on public (master) branches.
+
+#. You submit a change.
+
+#. Somebody else submits a change and that change merges.
+   Now your change has a merge conflict.
+
+#. Update your local repository:
+
+   .. code-block:: console
+
+      $ git remote update
+      $ git pull --ff-only origin master
+
+#. Download your change:
+
+   .. code-block:: console
+
+      $ git review -d $PARENT_CHANGE_NUMBER
+
+#. Rebase your change:
+
+   .. code-block:: console
+
+      $ git rebase origin/master
+
+
+#. Resolve conflicts manually:
+
+   Conflicts are marked in a file with clear line breaks:
+
+   .. code-block:: console
+
+      <<<<<<< HEAD
+      Second line.
+      =======
+      Third line.
+      >>>>>>> feature/topic branch.
+
+   <<<<<<<: Indicates the start of the lines that had a merge conflict.
+
+   =======: Indicates separation of the two conflicting changes.
+
+   >>>>>>>: Indicates the end of the lines that had a merge conflict.
+
+   You need to resolve a conflict by manually editing the file.
+   You also need to delete the '<<<<<<<', '=======', and'>>>>>>>'
+   in the file. Add the files to the stage by
+   running :command:`git add <filename>`.
+
+#. Commit the changes:
+
+   .. code-block:: console
+
+      $ git commit
+
+#. Complete the rebase process:
+
+   .. code-block:: console
+
+      $ git rebase --continue
+
+#. Send the rebased patch again for review:
+
+   .. code-block:: console
+
+      $ git review
+