Support native Git LFS File locking

Description

Git LFS has released file locking. It's only possible through the CLI. We do support File locking, but only through the GUI. Can our GUI use native Git LFS v2 to support file locking?

Source

Git LFS file locking: https://github.com/blog/2328-git-lfs-2-0-0-released

changed title from Support Git LFS File locking to Support native Git LFS File locking

@DouweM @vsizov @rspeicher thoughts?

@chriscool also you

This will soon become a must-have for Game Dev with Unity (plugin available in alpha) and Unreal Engine (dev in progress).

@regisF We can implement the LFS locking API to work with our existing file locking feature, which means locks in the web UI translate to git lfs locks, and git lfs locks translate to GUI locks.

@mydigitalself We should definitely do this in the not too far off future!

@regisF Are we going to bring File Locks to CE now?

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@DouweM I'm not sure we should. We need to keep features part of EE. The added value of this updated feature is to use a GUI for it.

I think it is already clear, but in case it is not:

1. You should update you LFS implementation in CE, upgrading the API from LFS 1.x to 2.x, to support git lfs locks.
2. You can keep the File Locks UI in EE as an added value.

@regisF I vaguely remember @JobV mentioning somewhere that we'd move locks to CE if LFS shipped with it natively.

@DouweM @mydigitalself @regisF I would like it to be EE exclusive, but I don't see how that would work with a native Git LFS implementation.

I think the comment of @sebastien-rombauts makes sense. File locks in UI should stay in EE. Thanks Sebastien!

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I noticed the milestone was pushed back, did you encounter problems? Maybe others can help.

@fire no problems, just some other priorities needed addressing first. Revisiting scheduling this in 9.5, where I've put it for now until we do 9.5 planning.

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Hey. Is LFS v.2.0 with File Locking Ability going to implemented by now? This would be a great future that would make GIT also attractive for all developers who are afraid of getting merge conflicts with complicated binary files, e.g. Simulink Models or Excel Files.

@GMaggi89 agreed. Having LFS 2.x in GitLab (CE) would make it very attractive for model based development.

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More interest in Git LFS File Locking: https://gitlab.zendesk.com/agent/tickets/81978

Sadly we're very constrained at the moment owing to a lot of work happening in Geo so moving this out a few releases :(

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Not supporting LFS 2.X makes it very difficult to use LFS with GitLab. Even from the command line on OSX, it's complicated to install LFS 1.5.6 instead of 2.x. Please get this support added to Gitlab-ee ASAP.

mentioned in commit f7efd265

mentioned in commit 87c67b17