Merge branch 'hn/branch-delete-merged' into seen

The 'git branch' command has been taught the '--delete-merged' option to remove local branches that are already merged into their tracked remote-tracking branches. * hn/branch-delete-merged: branch: add --dry-run for --delete-merged branch: add branch.<name>.deleteMerged opt-out branch: add --delete-merged <pattern> branch: prepare delete_branches for a bulk caller branch: let delete_branches skip unmerged branches on bulk refusal branch: convert delete_branches() to a flags argument branch: add --forked filter for --list mode