File Lock

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/497

• Data layer(tables, models, migrations)
• Checks on git push
• Author should be able to push if one owns the lock
• Path matcher with tokenizer and memoization
• Show lock status icons by files and folders
• UI: mockup buttons for locking files, folders
• UI: Locking files
• UI: Locking folders
• Permissions check everywhere
• Add page to list all locked files/dirs to get overview in case people forget to unlock
• Refactor lock_file_button and lock_file_link
• Testing Git LFS
• Get rid of code duplication in pre-receive hook
• Test case: I want to unlock file if I'm a developer and I'm not an author of lock
• Make it EE option
• Specs and spinach
• TODOs in the code

Can be moved to the next iteration:

• Fix Web UI lock check(!487 (merged))
• timeago in the lock icon tooltip. It's not working out of the box(#704)
• Ajax load bar on click "Lock/Unlock" in the file tree (#698 (closed))
• Nested locking UI. If we look at file and it's locked because of parent we should show it in tooltip. (#705 (closed))

Screenshots

Related info: Douwe wrote: For a next iteration, we need to think about nested locking more. If user A has locked lib/, user B shouldn't be able to lock lib/foo.rb since that falls under lib/. Similarly, if user A has locked lib/foo.rb, user B shouldn't be able to lock lib/, because part of that directory is locked by someone else already.