Here is a helpful checklist to go through before uploading change lists (CLs) on Gerrit, which is the code review platform for the Chromium project. This checklist is designed to be streamlined. See contributing to Chromium for a more thorough reference. The intended audience is software engineers who are unfamiliar with contributing to the Chromium project.
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You should create a new branch before starting any development work. It's helpful to branch early and to branch often in Git.
git new-branch <branch_name>
which is equivalent to
git checkout -b <branch_name> --track origin/master
Mark the associated crbug as "started" so that other people know that you have started work on the bug. Doing this can avoid duplicated work.
Do your thing. There's no further advice here about how to write or fix code.
After making your changes, check that common targets build correctly:
- chrome (for Linux, ChromeOS, etc.)
- unit_tests
- browser_tests
It's easy to inadvertently break one of the other builds you're not currently working on without realizing it. Even though the Commit Queue should catch any build errors, checking locally first can save you some time since the CQ Dry Run can take a while.
Make sure you hit every code path you changed.
Consider automating any manual testing you did in the previous step.
Run git cl format --js. The --js option also formats JavaScript changes.
Run git upstream-diff to check over all of the changes you've made from the
most recent checkpoint on the remote repository.
Run git add <path_to_file> for all of the relevant files you've modified.
Unlike other version-control systems such as svn, you have to specifically git add the files you want to commit before calling git commit.
Run git commit. Here are some
tips for writing good commit messages.
If you have many commits on your current branch, and you want to avoid some
nasty commit-by-commit merge conflicts in the next step, it is recommended to
squash your commits into a single commit. This is done by running git rebase -i <upstream-branch>. The upstream branch is usually origin/master, but check git branch -vv to make sure. After running the git rebase command, you should see a
list of commits, each commit starting with the word "pick". Make sure the first
commit says "pick" and change the rest from "pick" to "squash". This will squash
each commit into the previous commit, which will continue until each commit is
squashed into the first commit.
Run git rebase-update. This command updates all of your local branches with
remote changes that have landed since you started development work, which
could've been a while ago. It also deletes any branches that match the remote
repository, such as after the CL associated with that branch had merged. You may
run into rebase conflicts which should be manually fixed before proceeding with
git rebase --continue. Rebasing prevents unintended changes from creeping into
your CL.
Note that rebasing has the potential to break your build, so you might want to try re-building afterwards.
Run git cl upload. Some useful options include:
--cq-dry-run(or-d) will set the patchset to do a CQ Dry Run.-r <chromium_username>will add reviewers.-b <bug_number>automatically populates the bug reference line of the commit message.
Run git cl web to go to the Gerrit URL associated with the current branch.
Open the latest patch set and verify that all of the uploaded files are correct.
Click Expand All to check over all of the individual line-by-line changes
again.
Click CQ Dry Run. Fix any errors because otherwise the CL won't pass the
commit queue (CQ) checks. Consider waiting for the CQ Dry Run to pass before
notifying your reviewers, in case the results require major changes in your CL.
Click Find Owners or run git cl owners to find file owners to review your
code and instruct them about which parts you want them to focus on. Add anyone
else you think should review your code. The blame functionality in Code Search
is a good way to identify reviewers who may be familiar with the parts of code
your CL touches. For your CL to land, you need an approval from an owner for
each file you've changed, unless you are an owner of some files, in which case
you don't need separate owner approval for those files.
Then go through this commit checklist again. Reply to all comments from the
reviewers on Gerrit and mark all resolved issues as resolved (clicking Done or
Ack will do this automatically). Click Reply to ensure that your reviewers
receive a notification. Doing this signals that your CL is ready for review
again, since the assumption is that your CL is not ready for review until you
hit reply.
Once you have obtained a Looks Good To Me (LGTM), which is reflected by a
Code-Review+1 in Gerrit, from at least one owner for each file, then you have
the minimum prerequisite to land your changes. It may be helpful to wait for all
of your reviewers to approve your changes as well, even if they're not owners.
Click Submit to CQ to try your change in the commit queue (CQ), which will
land it if successful.
After your CL is landed, you can use git rebase-update or git cl archive to
clean up your local branches. These commands will automatically delete merged
branches. Mark the associated crbug as "fixed".