56 lines
2.7 KiB
Markdown
56 lines
2.7 KiB
Markdown
I'm considering ways to get rid of direct mode, replacing it with something
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better implemented using [[todo/smudge]] filters.
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## git-lfs
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I started by trying out git-lfs, to see what I can learn from it. My
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feeling is that git-lfs brings an admirable simplicity to using git with
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large files. For example, it uses a push-hook to automatically
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upload file contents before pushing a branch.
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But its simplicity comes at the cost of being centralized. You can't make a
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git-lfs repository locally and clone it onto other drive and have the local
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repositories interoperate to pass file contents around. Everything has to
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go back through a centralized server. I'm willing to pay complexity costs
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for decentralization.
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Its simplicity also means that the user doesn't have much control over what
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files are present in their checkout of a repository. git-lfs downloads
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all the files in the work tree. It doesn't have facilities for dropping
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files to free up space, or for configuring a repository to only want to get
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a subset of files in the first place. Some of this could be added to it
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I suppose.
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## replacing direct mode
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Anyway, as smudge/clean filters stand now, they can't be used to set up
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git-annex symlinks; their interface doesn't allow it. But, I was able to
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think up a design that uses smudge/clean filters to cover the same use
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cases that direct mode covers now.
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Thanks to the clean filter, adding a file with `git add` would check in a
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small file that points to the git-annex object. When a file has been added
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this way, the file in the work tree remains the only copy of the object
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until you use git-annex to copy it to another repository. So if you modify
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the work tree file, you can lose the old version of the object.
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This is analagous to how direct mode works now, and it avoids needing to
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store 2 copies of every file in the local repository.
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In the same repository, you could also use `git annex add` to check
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in a git-annex symlink, which would protect the object from modification,
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in the good old indirect mode way. `git annex lock` and `git annex unlock`
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could switch a file between those two modes.
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So this allows mixing directly writable annexed files and locked down
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annexed files in the same repository. All regular git commands and all
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git-annex commands can be used on both sorts of files.
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That's much more flexible than the current direct mode, and I think it will
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be able to be implemented in a simpler, more scalable, and robust way too.
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I can lose the direct mode merge code, and remove hundreds of lines of
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other special cases for direct mode.
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The downside, perhaps, is that for a repository to be usable on a crippled
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filesystem, all the files in it will need to be unlocked. A file can't
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easily be unlocked in one checkout and locked in another checkout.
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