Merge branch 'es/worktree-avoid-duplication-fix'

In rare cases "git worktree add <path>" could think that <path>
was already a registered worktree even when it wasn't and refuse
to add the new worktree. This has been corrected.

* es/worktree-avoid-duplication-fix:
  worktree: don't allow "add" validation to be fooled by suffix matching
  worktree: add utility to find worktree by pathname
  worktree: improve find_worktree() documentation

diff --cc worktree.c
Simple merge