Remove non-existing remote branches:

git fetch --prune
git config remote.origin.prune true

Find commits using a keyword search:

git log -g --grep='findme'

Delete a tag:

• https://nathanhoad.net/how-to-delete-a-remote-git-tag
• http://stackoverflow.com/questions/5480258/how-to-delete-a-remote-tag

git tag -l 
git tag -d 12345
git push origin :refs/tags/12345
git log master..Release-1.11.0 \| grep 'luke'