Merge branch 'ds/branch-checked-out'

Introduce a helper to see if a branch is already being worked on (hence should not be newly checked out in a working tree), which performs much better than the existing find_shared_symref() to replace many uses of the latter. * ds/branch-checked-out: branch: drop unused worktrees variable fetch: stop passing around unused worktrees variable branch: fix branch_checked_out() leaks branch: use branch_checked_out() when deleting refs fetch: use new branch_checked_out() and add tests branch: check for bisects and rebases branch: add branch_checked_out() helper