44 lines
2.1 KiB
Markdown
44 lines
2.1 KiB
Markdown
This page gives a high-level view of how git-annex works. For a detailed
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low-level view, see [[the_man_page|git-annex]] and [[internals]].
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You do not need to read this page to get started with using git-annex. The
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[[walkthrough]] provides step-by-step examples, and [[workflow]] discusses
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different ways you can use git-annex.
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----
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Still reading? Ok. Git's man page calls it "a stupid content
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tracker". With git-annex, git is instead "a stupid filename and metadata
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tracker". The contents of annexed files are not stored in git, only the
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names of the files and some other metadata remain there.
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The contents of the files are kept by git-annex in a distributed key/value
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store consisting of every clone of a given git repository. That's a fancy
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way to say that git-annex stores the actual file content somewhere under
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`.git/annex/`. (See [[internals]] for details.)
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That was the values; what about the keys? Well, a key is calculated for a
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given file when it's first added into git-annex. Normally this uses a hash
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of its contents, but various [[backends]] can produce different sorts of
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keys. The file that gets checked into git is just a symlink to the key
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under `.git/annex/`. If the content of a file is modified, that produces
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a different key (and the symlink is changed).
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A file's content can be [[transferred|transferring_data]] from one
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repository to another by git-annex. Which repositories contain a given
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value is tracked by git-annex (see [[location_tracking]]). It stores this
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tracking information in a separate branch, named "git-annex". All you ever
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do with the "git-annex" branch is push/pull it around between repositories,
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to [[sync]] up git-annex's view of the world.
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That's really all there is to it. Oh, there are [[special_remotes]] that
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let values be stored other places than git repositories (anything from
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Amazon S3 to a USB key), and there's a pile of commands listed in
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[[the_man_page|git-annex]] to handle moving the values around and managing
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them. But if you grok the description above, you can see through all that.
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It's really just symlinks, keys, values, and a git-annex branch to store
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additional metadata.
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---
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Next: [[install]] or [[walkthrough]]
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