Comment by wyoung2 | Hacker News Reader

Comment by wyoung2 | Hacker News Reader

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> I’d guess not one user in 100.000 uses git decentralized

I understand your sentiment, but the denominator in that fraction is probably much lower than your guess.

Consider even simple cases like the disconnected laptop case. You may work at a small office with only local employees, and so you have one central "blessed" repo, but if one person locks a file and then goes off to lunch, working on the file while at the restaurant, you still have a CAP problem:

CA: Because the one guy with a laptop went off-network, you have no full quorum, so no one can use the repo at all until he gets back and rejoins the network. (No practical DVCS does this, but it's one of the options, so I list it.)

CP: When the one guy went off to lunch, we lost the ability to interact with his lock, and that will continue to be the case until he gets back from lunch. Also vice versa: if someone still at the office takes out a lock, the guy off at lunch doesn't realize there is lock, so he could do something bad with the "locked" file. (This is the mode DVCSes generally run in by default.)

AP: No locking at all, thus no consistency, thus your original problem that inspired the wish to have file locking.

Not sure I understand the problem. If I lock fileX and go to lunch, then I own the lock on that file while I’m out to lunch. It’s basically analogous me pushing the file fileX.lock to the repo next to fileX, with my user id as content. I can only do it if it isn’t there.

Everyone else will only see that lock if they fetch and if they don’t, they might edit their local copy of fileX too, but would be prevented from pushing their version to the blessed repository by the lock. They can push a copy under another name, or wait until I have removed the lock (but probably can’t resolve the conflict anyway because it’s likely a binary document). So they user will remember to never start editing without taking the lock in the future.

It’s not perfect by any stretch of the imagination but it’s all anyone asks for in terms of file locking. It’s what Subversion always did.

> Not sure I understand the problem. If I lock fileX and go to lunch, then I own the lock on that file while I’m out to lunch.

And if you go on vacation for two weeks instead?

Same thing obviously. But this is just a method of communication. It’s instead of emailing/shouting “don’t edit the background image today please” across the office.

An admin can remove the lock. Or you can allow force-pushing by anyone to replace it or whatever.

Not sure why this is seen as so complicated, version control systems have done it since forever. It’s not trying to solve some distributed lock system in a clever way. It’s dumb centralized mutex per file. And yet again this is all that’s needed (and it’s also added to git in git-LFS!).

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