HotFix Guide

HotFix general instructions

The following instructions intend to be general case for applying hotfixes in release branches, for more specific cases, simplified instructions are to be found in the below sub-sections.

Find the oldest relevant release branch BASE to which this hotfix applies.
- Relevant release branches include: release, and release-specific maintained branches.
Create a hotfix branch branching from BASE.
- if the hotfix branch already exists git rebase --onto BASE.
Open a merge-request targeting:
- master, if applies to master.
- Otherwise, release, if applies to the latest release.
- Otherwise, the most recent release-specific branch to which this hotfix applies.
- Lastly, if none of above, BASE.
(If needed) If the hotfix is a backport (cherry-picked) of an existing merge-requests, add a cross-reference each of the existing merge-request with the format of !1234 inside the description of the newly created merge-request.
- Cherry-pick each of the relevant commits of the existing merge-requests using git cherry-pick -x XXYYZZ.
At the bottom of the description of the merge-request add: Backport: branch_name directive for each of the branches that exists between BASE (inclusive) and the branch that we target our merge-request (exclusive).

In the case of merge conflicts in any of the backports refer to Kitware backport guide.

HotFix for latest release and master branch only

For hotfixes that applies to release and master branch, create a branch based off of the tip of the release branch and create a merge-request targeting master.

If the hotfix branch already exists based off of a commit in the master branch, you can change the base branch of the hotfix branch from master to latest release with:

# Assuming that both your local master and release branch are updated; and
# assuming that you are currently in your topic branch

git rebase --onto release master

Next, you can bring this commit to release by adding the following line to the bottom of the MR description: Backport: release. This directive will later internally instruct the Kitware Robot to bring the changes of the hotfix branch creating a merge commit in the release branch with its second parent being the hotfix branch tip.

Lastly, the master branch history will be automatically connected with release after the merge-request is merged as explained in here.

HotFix for release branch only

For hotfixes that only applies to release branch, whose changes are unneeded in master, create a branch based off of the release branch and create a merge-request targeting release branch. Proceed as in a regular MR.

How master and release branch are connected

Every merge commit in the release branch will be automatically connected to master branch by our Gitlab robot creating a merge-request using the -s ours strategy, note that -s ours strategy does not actually bring any change to the target branch, it will solely create an empty merge commit in master connecting release branch..

Other cases

There are more possible case scenarios that you might encounter while attempting to bring a hotfix to release, for further cases please refer to the Kitware backport guide which this document is based of.

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