git-annex tries to ensure that the configured number of copies of your data always exist, and leaves it up to you to use commands like git annex get and git annex drop to move the content to the repositories you want to contain it. But often, it can be good to have more fine-grained control over which content is wanted by which repositories. Configuring this allows the git-annex assistant as well as git annex get --auto, git annex drop --auto, git annex sync --content, etc to do smarter things.

Preferred content settings can be edited using git annex vicfg, or viewed and set at the command line with git annex wanted. Each repository can have its own settings, and other repositories will try to honor those settings when interacting with it. (So there's no local .git/config for preferred content settings.)

The idea is that you write an expression that files are matched against. If a file matches, the repository wants to store its content. If it doesn't, the repository wants to drop its content (if there are enough copies elsewhere to allow removing it).

writing expressions

quickstart

Rather than writing your own preferred content expression, you can use several standard ones included in git-annex that are tuned to cover different common use cases.

You do this by putting a repository in a group, and simply setting its preferred content to "standard" to match whatever is standard for that group. See standard groups for a list.

See the man page git-annex-preferred-content for details on the syntax of preferred content expressions.

An example:

include=*.mp3 and (not largerthan=100mb) and exclude=old/*

This makes all .mp3 files, and all other files that are less than 100 mb in size be preferred content. It excludes all files under the "old" directory.

upgrades

It's important that all clones of a repository can understand one-another's preferred content expressions, especially when using the git-annex assistant. So using newly added keywords can cause a problem if an older version of git-annex is in use elsewhere.

Before git-annex version 5.20140320, when git-annex saw a keyword it did not understand, it defaulted to assuming all files were preferred content. From version 5.20140320, git-annex has a nicer fallback behavior: When it is unable to parse a preferred content expression, it assumes all files that are currently present are preferred content.

Here are recent changes to preferred content expressions, and the version they were added in.

  • "nothing" 6.201600202
  • "anything" 5.20150616
  • "standard" 5.20140314
    (only when used in a more complicated expression; "standard" by itself has been supported for a long time)
  • "groupwanted=" 5.20140314
  • "metadata=" 5.20140221
  • "lackingcopies=", "approxlackingcopies=", "unused=" 5.20140127
  • "inpreferreddir=" 4.20130501
  • "metadata=field<number" etc 6.20160227