To update the local list of remote branches
git remote update origin --prune
Listing branches with their latest author
git for-each-ref --format='%(committerdate) %09 %(authorname) %09 %(refname)'
Find all repos (eg current_dir/group/repo)
find . -mindepth 3 -maxdepth 3 -name '.git' -execdir pwd \; -execdir git for-each-ref --format='%(committerdate) %09 %(authorname) %09 %(refname)' \;