Newcomer question

Hi GHC Devs, I just joined the community and wanted to start contributing/hacking on GHC. I was going through Newcomer's Info tab, and this https://ghc.haskell.org/trac/ghc/ticket/8811 seemed like a good first thing for me to try. A few questions related to git: from the ticket it looks like this bug happens in 7.6.3. From the repo I checked out, there is a tag ghc-7.6.3-release. But I guess I'm not really supposed to checkout the tag and modify the code from there? But running git branch only shows the master branch. So should I run ./sync-all checkout ghc-7.6 and modify the code from that branch? Thank you very much! Best, Hengchu