TVL Code Reviews

Table of Contents

TVL Code Reviews

This document describes the TVL code review process & tooling. If you are looking for general contribution guidelines, please look at the general contribution guidelines.

All changes are tracked at cl.tvl.fyi using Gerrit. See Registration for information on how to register an account.

Gerrit setup

Gerrit uses the concept of change IDs to track commits across rebases and other operations that might change their hashes, and link them to unique changes in Gerrit.

First, tell Gerrit about your SSH keys.

Then, to make using Gerrit smooth for users, the repository should be cloned and a commit hook should be installed as follows:

git clone "ssh://$USER@code.tvl.fyi:29418/depot"
curl -Lo depot/.git/hooks/commit-msg https://cl.tvl.fyi/tools/hooks/commit-msg
chmod +x depot/.git/hooks/commit-msg

If you have a previous clone of the depot via HTTP you can use git remote set-url to update the origin URL and install the hook in the same way as above.

Gerrit workflows

The developer workflow on Gerrit is quite different from what GitHub-users are used to.

Instead of pushing changes to remote branches, all changes have to be pushed to refs/for/canon. For each commit that is pushed there, a change request is created automatically.

Changes should usually be based on the remote HEAD (the canon branch).

Every time you create a new commit the change hook will insert a unique Change-Id tag into the commit message. Once you are satisfied with the state of your commit and want to submit it for review, you push it to a git ref called refs/for/canon. This designates the commits as changelists (CLs) targeted for the canon branch.

Sending a change for review is done by pushing to a special target. You can set this to be the default push target through your git configuration:

git config remote.origin.url "ssh://$USER@code.tvl.fyi:29418/depot"
git config remote.origin.push HEAD:refs/for/canon

Then, after making your change, push to the default, or to a special target:

Example:
git commit -m 'docs(REVIEWS): Fixed all the errors in the reviews docs'
git push origin

# Uploading a work-in-progress CL:
git push origin HEAD:refs/for/canon%wip

TIP: Every individual commit will become a separate change. We do not squash related commits, but instead submit them one by one. Be aware that if you are expecting a different behaviour and attempt something like an unsquashed subtree merge, you will produce a lot of CLs. This is strongly discouraged.

During your review, the reviewer(s) might ask you to make changes. You can simply amend your commit(s) and push to the same ref. Gerrit will automatically update your changes.

Read more about the Gerrit workflow in the Gerrit walkthrough.

Review process & approvals

Each user has the ability to create their own users directory in //users/<username> in which they can submit code without review from other contributors (they will still need to +2 their own changes, and the initial check-in of the OWNERS file needs to be reviewed).

You can set a directory like this up for yourself by proposing a change similar to CL/246.

For all paths outside of //users, code review is required. We have no strict guidelines about the review process itself, as we're not a megacorp, but we have formalised checks before submitting:

At least one person who is an owner of the codepath must have given a +2 review
The commit message must conform to our guidelines
No code review comments must be left unresolved

If all these conditions are fulfilled, the change author submits their change themselves.

Registration

You may log into Gerrit using a GitHub, StackOverflow or GitLab.com account.

If you would like to have a TVL-specific account on the Gerrit instance, follow these instructions:

Be a member of #tvl on hackint.
Clone the depot locally (via git clone "https://cl.tvl.fyi/depot").
Create a user entry in our LDAP server in ops/users.

The entry can be generated using //web/pwcrypt.
Create a commit adding yourself (see e.g. CL/2671)
Submit the commit via email (see below).

Submitting changes via email

Please keep in mind this process is more complicated and requires more work from both sides:

Someone needs to relay potential comments from Gerrit to you, you won't get emails from Gerrit.
Uploading new revisions needs to be done by the person sending it to Gerrit on your behalf.
If you decide to get a Gerrit account later on, existing CLs need to be abandoned and recreated (as CLs can't change Owner). This causing earlier reviews do be more disconnected, causing more churn.

We provide local accounts and do SSO with various third-parties, so getting the account should usually be low-friction.

If you still decide differently, you can submit a patch via email to depot@tvl.su and it will be added to Gerrit by a contributor.

Create an appropriate commit locally and send it us using either of these options:

git format-patch: This will create a .patch file which you should email to us.
git send-email: If configured on your system, this will take care of the whole emailing process for you.

The email address is a public inbox.

Gerrit for Github Users

There is a walkthrough that describes only the parts that differ from Github, although it does not cover attention sets, which are important to understand.

Attention Sets

The attention set of a CL is somewhat similar to the set of Github users who have unread notifications for a PR. The "your turn" list on the dashboard is similar to your unread notifications list in Github. These similarities are only rough approximations, however.

Unfortunately the rules for updating attention sets are very different and complex. If you don't read and understand them, you may end up leaving comments that nobody ever finds out about. Here are a few unexpected features:

Voting on or replying to a CL will remove you from the attention set. You can also do this by clicking on the gray chevron shape next to your name.
If you comment on a merged or abandoned change without marking your comment "unresolved", nobody will be notified of your comment. If you want to the owner of a merged or abandoned change to read your comment, you must mark it as "unresolved" or manually add them to the attention set by hovering your mouse over their name and clicking "add to attention set"

There are many more rules, which you should read.