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 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
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).
finding preferred content
To check at the command line which files are matched by preferred content settings, you can use the --want-get and --want-drop options.
git annex find --want-get --not --in . will find all the
git annex get --auto will want to get, and
git annex find
--want-drop --in . will find all the files that
git annex drop --auto
will want to drop.
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.
The expressions are very similar to the matching options documented on the git-annex-matching-options man page. At the command line, you can use those options in commands like this:
git annex get --include='*.mp3' --and -'(' --not --largerthan=100mb -')'
The equivalent preferred content expression looks like this:
include=*.mp3 and (not largerthan=100mb)
So, just remove the dashes, basically. But, there are some differences between the command line options and expressions, so see the documentation below to get the full story.
Match files to include, or exclude.
While --include=glob and --exclude=glob match files relative to the current directory, preferred content expressions always match files relative to the top of the git repository.
For example, suppose you put files into
archivedirectories when you're done with them. Then you could configure your laptop to prefer to not retain those files, like this:
Matches only files that git-annex believes to have the specified number of copies, or more. Note that it does not check remotes to verify that the copies still exist.
To decide if content should be dropped, git-annex evaluates the preferred content expression under the assumption that the content has already been dropped. If the content would not be wanted then, the drop can be done. So, for example,
copies=2in a preferred content expression lets content be dropped only when there are currently 3 copies of it, including the repo it's being dropped from. This is different than running
git annex drop --copies=2, which will drop files that currently have 2 copies.
Matches only files that git-annex believes have the specified number copies, on remotes with the specified trust level. For example,
To match any trust level at or higher than a given level, use
trustlevel+. For example,
Matches only files that git-annex believes have the specified number of copies, on remotes in the specified group. For example,
Preferred content expressions have no equivilant to the
--inoption, but groups can accomplish similar things. You can add repositories to groups, and match against the groups in a preferred content expression. So rather than
--in=usbdrive, put all the USB drives into a "transfer" group, and use
Matches only files that git-annex believes need the specified number or more additional copies to be made in order to satisfy their numcopies settings.
Like lackingcopies, but does not look at .gitattributes annex.numcopies settings. This makes it significantly faster.
Matches only files whose content is stored using the specified key-value backend.
Matches only files that git-annex believes are present in all repositories in the specified group.
Matches only files whose content is smaller than, or larger than the specified size.
The size can be specified with any commonly used units, for example, "0.5 gb" or "100 KiloBytes"
Matches only files that have a metadata field attached with a value that matches the glob. The values of metadata fields are matched case insensitively.
To match a tag "done", use
To match author metadata, use
Makes content be wanted if it's present, but not otherwise.
This leaves it up to you to use git-annex manually to move content around. You can use this to avoid preferred content settings from affecting a subdirectory. For example:
auto/* or (include=ad-hoc/* and present)
not presentis a very bad thing to put in a preferred content expression. It'll make it want to get content that's not present, and drop content that is present! Don't go there..
Makes content be preferred if it's in a directory (located anywhere in the tree) with a particular name.
The name of the directory can be configured using
git annex enableremote $remote preferreddir=$dirname
(If no directory name is configured, it uses "public" by default.)
git-annex comes with some built-in preferred content expressions, that can be used with repositories that are in some standard groups.
When a repository is in exactly one such group, you can use the "standard" keyword in its preferred content expression, to match whatever content the group's expression matches. (If a repository is put into multiple standard groups, "standard" will match anything.. so don't do that!)
Most often, the whole preferred content expression is simply "standard". But, you can do more complicated things, for example:
standard or include=otherdir/*
The "groupwanted" keyword can be used to refer to a preferred content expression that is associated with a group. This is like the "standard" keyword, but you can configure the preferred content expressions using
git annex groupwanted.
Note that when writing a groupwanted preferred content expression, you can use all of the keywords listed above, including "standard". (But not "groupwanted".)
For example, to make a variant of the standard client preferred content expression that does not want files in the "out" directory, you could run:
git annex groupwanted client "standard and exclude=out/*"
Then repositories that are in the client group and have their preferred content expression set to "groupwanted" will use that, while other client repositories that have their preferred content expression set to "standard" will use the standard expression.
Or, you could make a new group, with your own custom preferred content expression tuned for your needs, and every repository you put in this group and make its preferred content be "groupwanted" will use it.
For example, the archive group only wants to archive 1 copy of each file, spread among every repository in the group. Here's how to configure a group named redundantarchive, that instead wants to contain 3 copies of each file:
git annex groupwanted redundantarchive "not (copies=redundantarchive:3)" for repo in foo bar baz; do git annex group $repo redundantarchive git annex wanted $repo groupwanted done
Matches only keys that
git annex unusedhas determined to be unused.
This is related the the --unused option. However, putting
unusedin a preferred content expression doesn't make git-annex consider those unused keys. So when git-annex is only checking preferred content expressions against files in the repository (which are obviously used),
unusedin a preferred content expression won't match anything.
So when is
unuseduseful in a preferred content expression?
git annex sync --content --allwill operate on all files, including unused ones, and take
unusedin preferred content expressions into account.
- The git-annex assistant periodically scans for unused files, and moves them to some repository whose preferred content expression says it wants them. (Or, if annex.expireunused is set, it may just delete them.)
Matches any version of any file.
Inverts what the expression matches. For example,
not include=archive/*is the same as
( expression )
These can be used to build up more complicated expressions.
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.
- "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