If you have a patch to the master branch (e.g. an important bug fix) that needs to be merged into one of the production V8 branches, read on.
For the examples, a branched 2.4 version of V8 will be used. Substitute “2.4” with your version number. See [[Release Process|Release Process]] for more information about version numbers.
An associated issue on Chromium‘s or V8’s issue tracker is mandatory if a patch is merged. This helps with keeping track of merges. You can use a template to create an issue.
The merge process in the Chromium and V8 tracker is driven by labels in the form of
The currently important labels for V8 are:
Use mergeinfo.py to get all the commits which are connected to the HASH according to Git.
If it tells you
Is on Canary: No Canary coverage you should not merge yet because the fix was not yet deployed on a Canary build. A good rule of the thumb is to wait at least 3 days after the fix has landed until the merge is conducted.
Let‘s assume you’re merging revision af3cf11 to branch 2.4 (please specify full git hashes - abbreviations are used here for simplicity).
tools/release/merge_to_branch.py --branch 2.4 af3cf11
Run the script with ‘-h’ to display its help message, which includes more options (e.g. you can specify a file containing your patch, or you can reverse a patch, specify a custom commit message, or resume a merging process you‘ve canceled before). Note that the script will use a temporary checkout of v8 - it won’t touch your work space. You can also merge more than one revision at once, just list them all.
tools/release/merge_to_branch.py --branch 2.4 af3cf11 cf33f1b sf3cf09
In case you are a V8 committer, feel free to use TBR to land the merge if it 1.) has approval and 2.) the merge was clean and no conflicts to resolve.
If one of the builders is not green after handling your patch, revert the merge immediately. A bot (AutoTagBot) will take care of the correct versioning after a 10 minute wait.
In case you need to patch a Canary/Dev version, which should not happen often follow these instructions:
Example version used is 2.4.4.
tools/release/roll_merge.py --branch 5.7.433 af3cf11
Example Chromium branch used is 2978
$ git checkout chromium/2978 $ git merge 5.7.433.1 $ git push
Chrome/Chromium should should pick of the change when they build automatically.