update-firefox-version.md

How to update Firefox version

Firefox releases new version every month and it is important for forks to update the upstream source as soon as possible for security reasons.

Process of the update is manual as some of the patches managed by minions may have to be rewritten.

Procedure is the following:

• update .workspace file with latest version of Firefox. It typically make sense to also bump version of the browser, eg. from 2021.01 to 2021.02
• run ./fern.js use to download Firefox source and update mozilla-release folder with it
• run ./fern.js import-patches - this step will likely fail

What to do with failing import-patches?

Fern imports all patches in a single operation but git will try to apply them one after other. In case of a failure git will exit with error but suggest next actions:

1. check the failing patch with git am --show-current-patch=diff and decide what to do
   1. if the patch is simple you can try to recreate from scratch in the current working tree
   2. if the patch is complext you can try to apply it manuall with help of git apply --verbose --reject ../patches/0018-Manual-override-of-search-engine-list.patch
2. git add your changes and when ready let git am to continue with next patch with git am --continue
3. do this until all patches are successfuly applied

This will result in a working tree that has all the patches but ./fern.js import-patches not fully done (for instance translations were not applied). To get to the clean state do:

• ./fern.js export-patches to get the updates patches into patches folder
• ./fern.js reset to clean the working tree - check git status if in fact it was propertly cleared
• ./fern.js import-patches should apply correcly this time (you may have to delete l10n-patches folder if it was present in repository root)

At this stage the update process is completed and is ready to be submitted as PR.

Remeber to update S3 cache in the .workspace so that CD can pick up Firefox source.