contrib: include branch name in file generated by start-backport

When working on backports to different branches, the generated file was
being overwritten as its name consisted of only the current date.
This commit changes the generated file name to also include information
about the branch/release in the file name to prevent this issue.

Signed-off-by: Robin Hahling <robin.hahling@gw-computing.net>

Documentation/contributing/release/backports.rst

@@ -119,9 +119,9 @@ Creating the backports branch
    .. note::
 
       This command will leave behind a file in the current directory with a
-      name based upon the current date in the form ``YYYY-MM-DD.txt`` which
-      contains a prepared backport pull-request description so you don't need
-      to write one yourself.
+      name based upon the release version and the current date in the form
+      ``vRELEASE-backport-YYYY-MM-DD.txt`` which contains a prepared backport
+      pull-request description so you don't need to write one yourself.
 
 #. Cherry-pick the commits using the master git SHAs listed, starting
    from the oldest (top), working your way down and fixing any merge
@@ -162,7 +162,8 @@ Via GitHub web interface
    backporting to. Note that by default Github creates PRs against the
    ``master`` branch, so you will need to change it. The title and
    description for the pull request should be based upon the
-   ``YYYY-MM-DD.txt`` file that was generated by the scripts above.
+   ``vRELEASE-backport-YYYY-MM-DD.txt`` file that was generated by the scripts
+   above.
 
 #. Label the new backport PR with the backport label for the stable branch such
    as ``backport/X.Y`` as well as ``kind/backports`` so that it is easy to find
@@ -179,12 +180,12 @@ Via command-line tools
 
 These steps require all of the tools described in the :ref:`backport_setup`
 section above. Note that the list of PRs to pass to the ``set-labels.py``
-script are listed at the end of the ``YYYY-MM-DD.txt`` file.
+script are listed at the end of the ``vRELEASE-backport-YYYY-MM-DD.txt`` file.
 
    .. code-block:: bash
 
       # Create a pull-request on Github
-      $ gh pull-request -b vX.Y -l backport/vX.Y -F YYYY-MM-DD.txt
+      $ gh pull-request -b vX.Y -l backport/vX.Y -F vRELEASE-backport-YYYY-MM-DD.txt
       # Set PR 1234's v1.0 backporting labels to pending
       $ contrib/backporting/set-labels.py 1234 pending 1.0
 

contrib/backporting/start-backport

@@ -36,4 +36,4 @@ fi
 
 DATE=$(date --rfc-3339=date)
 git checkout -b pr/v$BRANCH-backport-$DATE origin/v$BRANCH
-contrib/backporting/check-stable $BRANCH $DATE.txt
+contrib/backporting/check-stable $BRANCH v$BRANCH-backport-$DATE.txt