chore(common): remove --first-parent when searching for PRs
chore(common): remove --first-parent when searching for PRs

Instead of just reporting on --first-parent, now lists all merges that
are in the log, which means we get some non-PR merges but that's ok. At
least we get all of them.

This was most visible with chained PRs which were merged bottom-up.

tavultesoft/keymanweb,tavultesoft/keymanweb