Squashed 'maint-travis-ci/' content from commit 75aad7e

git-subtree-dir: maint-travis-ci
git-subtree-split: 75aad7e8ef3a8deab32cde7c352ccaf3781dae63
Merge commit '5a223ed929d3405b418056cd715dcfcf6a3809c0' as 'maint-travis-ci'
Enable travis
Reimplement in terms of Git::Ref