Previously, FETCH_HEAD would always point to tests-passed because our base docker image was configured to only fetch the tests-passed branch. Since https://github.com/discourse/discourse_docker/commit/53bbacc882, we switched to a partial clone which means that `git fetch; git checkout FETCH_HEAD` will checkout whichever remote branch is the first alphabetically. This commit makes the checkout more specific to avoid this issue.
* DEV: Update the working tree just once.
`git pull` was effectively doing `git fetch` and `git merge FETCH_HEAD`, and only then we were checking out the desired branch/commit. This change will skip the the merge step.
* DEV: Don't run lefthook in docker_test
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
David Taylor
Jarek Radosz
romanrizzi
Joffrey JAFFEUX
Sam Saffron
Penar Musaraj
Gerhard Schlager
Guo Xiang Tan
Robin Ward