At work, we use gerrit. It's different to git and to github, and we didn't get the right kind of training on howto use it. This is a self-assembled survival guide. If you can articulate the differences between a merge and a rebase then this is not for you!

Initial checkout

Your initial checkout should look something like this:

git clone ssh://you@gerrit.hostname:29418/project/sub-project && scp -p -P 29418 you@gerrit.hostname:hooks/commit-msg sub-project/.git/hooks/

You should then find yourself on the master branch.

You want to do some work

Create a local branch to do your work. Always. Do not create a remote branch - it's almost never worth it, and if you're reading this, you're doing the wrong thing ;-)

git checkout -b BUG-1234 origin/master

This creates, and checksout, a new branch called BUG-1234 based on the current master.

Do some work. Add, edit, delete some code. Then do the first checkin:

git add <changes>

git commit

Give your description. Now you might do some more work.

git add <new-changes>

git commit --amend

The core concept in gerrit seems to be that you only push a single commit. This means you need to modify/amend any pre-existing commits. gerrit itself sorts out the patch-sets when you push them, but you need to --amend locally when making your changes.

If it's been a while since you created the local branch, the origin/master may have changed. REBASE and NEVER MERGE:

git pull --rebase

When you merge you'll have a merge commit, that then means you have multiple commits. There are ways of dealing with this, but if you're reading this survival guide, they're not for you ;-)

If you have conflicts, fix them.

Finally, you've rebased, you're happy with both your changes and commit message: time to send your code to be reviewed:

git push origin HEAD:refs/for/master

Then, go fix up some reviewers, with at least one who has +2, and await feedback.

You have feedback from your reviews

Checkout your under-review branch. If you used a name like BUG-1234 this will be easy:

git checkout BUG-1234

Then, edit based on the feedback and treat these edits as "more work" on this branch. That means:

git add <review-changes>

git commit --amend

Update, if necessary, your commit message, but leave the ChangeId alone! Then, when ready:

git push origin HEAD:refs/for/master

Gerrit itself sorts out the patchsets - but you'll need to redo the reviewers sometimes.

You want to review someone else's work

Someone's asked you to review - best get it locally and see that it's up-to-snuff!

  • git checkout master (having first ensured that your git env is clean)
  • Find the "Download Checkout" link on the gerrit UI.
  • Paste that command at teh root of your checkout.
  • git checkout -b change-owner-bug-number (so that you can tell who this code came from)

Here you get to see the changes. If you want you could:

  • Make changes yourself
  • git add <your-changes>
  • git commit --amend
  • git push origin HEAD:refs/for/master

That will create another patchset for that review.

Survival!

With this cheatsheet, your changes of survival have gone way up. Gerrit seems to work best when you have local branches. You need for everything to be a single commit, but don't try squashing - always use --amend. Never do a merge either -- always use git pull --rebase. Some teams seem to have success when they configure their IDEs to run these commands, but I have personally seen too many cases where terrible commits were included because of this - so always use the git CLI :-)

Wed 2018-04-11

work unix git