Backporting Tickets to a Release Branch¶

So you have a ticket that you think should be backported to the release branch? What next? Note, these instructions use v88 as an alias for the release of the science pipelines to backport to. Replace the 88 with 24, 27, or whatever major release number we are on now.

First, add the label “backport-v88” to your jira ticket.

This will flag it for review by the DM-CCB. Continue merging your ticket to the default branch (main) and mark the ticket Done per instructions in the normal DM Development Workflow with Git, GitHub, JIRA and Jenkins.
Wait for approval. The ticket will gain the label “backport-approved.”
Checkout the release branch, v88.0.x, for each repo affected by your ticket.
```
git checkout v88.0.x
```
If the repo does not already have a v88.0.x branch, you need to create one based on v88.0.0.rc1 (not the latest rcN, although that should be identical):
```
git checkout v88.0.0.rc1
git checkout -b v88.0.x
git push -u origin v88.0.x
```
Now treat v88.0.x same as you would the default branch (main).
Create a copy of your ticket branch called tickets/DM-XXXXX-v88.
```
git checkout tickets/DM-XXXXX
git checkout -b tickets/DM-XXXXX-v88
git rebase --onto v88.0.x <sha_of_last_commit_before_your_branch>
```
In a new clone, this branch may not exist anymore if you have already merged your PR because merged branches may be automatically deleted. In this case, you can branch tickets/DM-XXXXX-v88 from v88.0.x, and cherry-pick the ticket commits.
```
git checkout v88.0.x
git checkout -b tickets/DM-XXXXX-v88
git cherry-pick <ticket commit>
```
The following may help you find your hash[es] from main: git show --quiet $(git log --oneline | grep 'Merge.*DM-XXXXX' | cut -d' ' -f1)^2
Resolve any rebase or cherry-pick problems depending on your method. Continue using the same procedure outlined in Review Preparation. Check that it cleanly builds via scons. There should be a latest shared v88.0.0.rcN stack on the development cluster. Run Jenkins. When running Jenkins, build against the release branch and rc1 even if later rcNs exist. The default SPLENV_REF may no longer be appropriate for v88.0.x. If you are unsure of the recommended env for the release, check with the release manager.
```
REFS: tickets/DM-XXXXX-v88 v88.0.x v88.0.0.rc1
PRODUCTS: lsst_distrib lsst_ci ci_imsim ci_hsc
SPLENV_REF: <default_or_recommended_for_release>
```
You may find that the ticket cannot be cleanly backported without first backporting another ticket.
When it passes, merge to v88.0.x using the same procedure outlined in Merging, including creating a pull request. On your pull request, remember to change the base branch to v88.0.x. If the backport was clean, you may self-review. If the backport was not clean and you would like another pair of eyes, you may ask someone to hit the “Approved” button on GitHub, but please do not put your ticket status back into In Review on Jira.
When merged to v88.0.x, label your Jira ticket backport-done.