Adding instructions for rebasing

As per bug, added instructions for manually rebasing a commit.

Change-Id: I0566fdfed9edb60b1c89a1c0c461e2e80467d5e6
Partial-Bug: #1673315

doc/source/developers.rst

@@ -573,6 +573,49 @@ you can use cross-repo dependencies (CRD) in Zuul:
 
 * These are one-way dependencies only -- do not create a cycle.
 
+
+Rebasing a commit
+-----------------
+
+Sometimes the target branch you are working on has changed, which can create
+a merge conflict with your patch. In this case, you need to rebase your
+commit on top of the current state of the branch. In many cases, this can be
+achieved by pressing the ``Rebase`` button in the gerrit interface. If this
+fails, you must rebase manually:
+
+#. Checkout and update master:
+
+   .. code-block:: console
+
+      $ git checkout master
+      $ git pull
+
+#. Checkout the working branch and rebase on master:
+
+   .. code-block:: console
+
+      $ git review -d 180503
+      $ git rebase origin/master
+
+#. If git indicates there are merge conflicts, view the affected files:
+
+   .. code-block:: console
+
+      $ git status
+
+#. Edit the listed files to fix conflicts, then add the modified files:
+
+   .. code-block:: console
+
+      $ git add <file1> <file2> <file3>
+
+#. Confirm that all conflicts are resolved, then continue the rebase:
+
+   .. code-block:: console
+
+      $ git status
+      $ git rebase --continue
+
 Gate Pipeline
 ^^^^^^^^^^^^^
 
@@ -792,8 +835,8 @@ If a change fails tests in Jenkins, please follow the steps below:
 
 A patchset has to be approved to run tests in the gate pipeline. If the
 patchset has failed in the gate pipeline (it will have been approved to get
-into the gate pipeline) a recheck will first run the check jobs and if those 
-pass, it will again run the gate jobs. There is no way to only run the gate 
+into the gate pipeline) a recheck will first run the check jobs and if those
+pass, it will again run the gate jobs. There is no way to only run the gate
 jobs, the check jobs will first be run again.
 
 More information on debugging automated testing failures can be found in the