rewrite so it's understandable without knowing about the related command-line options
This commit is contained in:
Joey Hess
parent
f77d485915
commit
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1 changed files with 158 additions and 102 deletions
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@ -39,8 +39,8 @@ files that `git annex get --auto` will want to get, and `git annex find
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will want to drop.
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The expressions are very similar to the matching options documented
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on the [[git-annex]] man page. At the command line, you can use those
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options in commands like this:
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on the [[git-annex-matching-options]] man page.
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At the command line, you can use those options in commands like this:
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git annex get --include='*.mp3' --and -'(' --not --largerthan=100mb -')'
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@ -48,152 +48,208 @@ The equivalent preferred content expression looks like this:
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include=*.mp3 and (not largerthan=100mb)
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So, just remove the dashes, basically. However, there are some differences
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from the command line options to keep in mind:
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So, just remove the dashes, basically. But, there are some differences
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between the command line options and expressions, so see the documentation
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below to get the full story.
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### difference: file matching
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## expressions
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While --include and --exclude match files relative to the current
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directory, preferred content expressions always match files relative to the
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top of the git repository.
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* `include=glob` and `exclude=glob`
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For example, suppose you put files into `archive` directories
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when you're done with them. Then you could configure your laptop to prefer
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to not retain those files, like this:
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Match files to include, or exclude.
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While --include=glob and --exclude=glob match files relative to the current
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directory, preferred content expressions always match files relative to the
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top of the git repository.
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For example, suppose you put files into `archive` directories
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when you're done with them. Then you could configure your laptop to prefer
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to not retain those files, like this:
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exclude=*/archive/*
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### difference: no "in="
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* `copies=number`
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Preferred content expressions have no direct equivalent to `--in`.
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Matches only files that git-annex believes to have the specified number
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of copies, or more. Note that it does not check remotes to verify that
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the copies still exist.
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Often, it's best to add repositories to groups, and match against
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the groups in a preferred content expression. So rather than
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`--in=usbdrive`, put all the USB drives into a "transfer" group,
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and use "copies=transfer:1"
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To decide if content should be dropped, git-annex evaluates the preferred
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content expression under the assumption that the content has *already* been
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dropped. If the content would not be wanted then, the drop can be done.
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So, for example, `copies=2` in a preferred content expression lets
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content be dropped only when there are currently 3 copies of it, including
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the repo it's being dropped from. This is different than running `git annex
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drop --copies=2`, which will drop files that currently have 2 copies.
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### difference: dropping
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* `copies=trustlevel:number`
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To decide if content should be dropped, git-annex evaluates the preferred
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content expression under the assumption that the content has *already* been
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dropped. If the content would not be wanted then, the drop can be done.
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So, for example, `copies=2` in a preferred content expression lets
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content be dropped only when there are currently 3 copies of it, including
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the repo it's being dropped from. This is different than running `git annex
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drop --copies=2`, which will drop files that currently have 2 copies.
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Matches only files that git-annex believes have the specified number
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copies, on remotes with the specified trust level. For example,
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`copies=trusted:2`
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### difference: "present"
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To match any trust level at or higher than a given level,
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use 'trustlevel+'. For example, `--copies=semitrusted+:2`
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There's a special "present" keyword you can use in a preferred content
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expression. This means that content is wanted if it's present,
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and not otherwise. This leaves it up to you to use git-annex manually
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to move content around. You can use this to avoid preferred content
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settings from affecting a subdirectory. For example:
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* `copies=groupname:number`
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Matches only files that git-annex believes have the specified number of
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copies, on remotes in the specified group. For example,
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`copies=archive:2`
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Preferred content expressions have no equivilant to the `--in`
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option, but groups can accomplish similar things. You can add
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repositories to groups, and match against the groups in a
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preferred content expression. So rather than `--in=usbdrive`,
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put all the USB drives into a "transfer" group, and use
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`copies=transfer:1`
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* `lackingcopies=number`
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Matches only files that git-annex believes need the specified number or
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more additional copies to be made in order to satisfy their numcopies
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settings.
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* `approxlackingcopies=number`
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Like lackingcopies, but does not look at .gitattributes annex.numcopies
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settings. This makes it significantly faster.
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* `inbackend=name`
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Matches only files whose content is stored using the specified key-value
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backend.
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* `inallgroup=groupname`
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Matches only files that git-annex believes are present in all repositories
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in the specified group.
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* `smallerthan=size` and `largerthan=size`
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Matches only files whose content is smaller than, or larger than the
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specified size.
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The size can be specified with any commonly used units, for example,
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"0.5 gb" or "100 KiloBytes"
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* `metadata=field=glob`
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Matches only files that have a metadata field attached with a value that
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matches the glob. The values of metadata fields are matched case
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insensitively.
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To match a tag "done", use `metadata=tag=done`
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To match author metadata, use `metadata=author=* Smith"
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* `present`
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Makes content be wanted if it's present, but not otherwise.
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This leaves it up to you to use git-annex manually
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to move content around. You can use this to avoid preferred content
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settings from affecting a subdirectory. For example:
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auto/* or (include=ad-hoc/* and present)
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Note that `not present` is a very bad thing to put in a preferred content
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expression. It'll make it want to get content that's not present, and
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drop content that is present! Don't go there..
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Note that `not present` is a very bad thing to put in a preferred content
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expression. It'll make it want to get content that's not present, and
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drop content that is present! Don't go there..
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### difference: "inpreferreddir"
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* `inpreferreddir`
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There's a special "inpreferreddir" keyword you can use in a
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preferred content expression of a special remote. This means that the
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content is preferred if it's in a directory (located anywhere in the tree)
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with a special name.
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Makes content be preferred if it's in a directory (located anywhere
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in the tree) with a particular name.
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The name of the directory can be configured using
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`git annex enableremote $remote preferreddir=$dirname`
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The name of the directory can be configured using
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`git annex enableremote $remote preferreddir=$dirname`
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(If no directory name is configured, it uses "public" by default.)
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(If no directory name is configured, it uses "public" by default.)
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### difference: "standard"
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* `standard`
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git-annex comes with some built-in preferred content expressions, that
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can be used with repositories that are in some [[standard_groups]].
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git-annex comes with some built-in preferred content expressions, that
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can be used with repositories that are in some [[standard_groups]].
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When a repository is in exactly one such group, you can use the "standard"
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keyword in its preferred content expression, to match whatever content
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the group's expression matches.
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(If a repository is put into multiple standard
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groups, "standard" will match anything.. so don't do that!)
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When a repository is in exactly one such group, you can use the "standard"
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keyword in its preferred content expression, to match whatever content
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the group's expression matches.
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(If a repository is put into multiple standard
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groups, "standard" will match anything.. so don't do that!)
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Most often, the whole preferred content expression is simply "standard".
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But, you can do more complicated things, for example:
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"`standard or include=otherdir/*`"
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Most often, the whole preferred content expression is simply "standard".
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But, you can do more complicated things, for example:
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`standard or include=otherdir/*`
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### difference: "groupwanted"
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* `groupwanted`
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The "groupwanted" keyword can be used to refer to a preferred content
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expression that is associated with a group. This is like the "standard"
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keyword, but you can configure the preferred content expressions
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using `git annex groupwanted`.
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The "groupwanted" keyword can be used to refer to a preferred content
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expression that is associated with a group. This is like the "standard"
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keyword, but you can configure the preferred content expressions
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using `git annex groupwanted`.
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Note that when writing a groupwanted preferred content expression,
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you can use all of the keywords listed above, including "standard".
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(But not "groupwanted".)
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Note that when writing a groupwanted preferred content expression,
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you can use all of the keywords listed above, including "standard".
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(But not "groupwanted".)
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For example, to make a variant of the standard client preferred content
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expression that does not want files in the "out" directory, you
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could run: `git annex groupwanted client "standard and exclude=out/*"`
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For example, to make a variant of the standard client preferred content
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expression that does not want files in the "out" directory, you
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could run: `git annex groupwanted client "standard and exclude=out/*"`
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Then repositories that are in the client group and have their preferred
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content expression set to "groupwanted" will use that, while
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other client repositories that have their preferred content expression
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set to "standard" will use the standard expression.
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Then repositories that are in the client group and have their preferred
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content expression set to "groupwanted" will use that, while
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other client repositories that have their preferred content expression
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set to "standard" will use the standard expression.
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Or, you could make a new group, with your own custom preferred content
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expression tuned for your needs, and every repository you put in this
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group and make its preferred content be "groupwanted" will use it.
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For example, the archive group only wants to archive 1 copy of each file,
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spread among every repository in the group.
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Here's how to configure a group named redundantarchive, that instead
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wants to contain 3 copies of each file:
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Or, you could make a new group, with your own custom preferred content
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expression tuned for your needs, and every repository you put in this
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group and make its preferred content be "groupwanted" will use it.
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For example, the archive group only wants to archive 1 copy of each file,
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spread among every repository in the group.
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Here's how to configure a group named redundantarchive, that instead
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wants to contain 3 copies of each file:
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git annex groupwanted redundantarchive "not (copies=redundantarchive:3)"
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for repo in foo bar baz; do
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git annex group $repo redundantarchive
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git annex wanted $repo groupwanted
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done
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### difference: metadata matching
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* `unused`
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This:
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Matches only keys that `git annex unused` has determined to be unused.
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git annex get --metadata tag=done
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This is related the the --unused option.
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However, putting `unused` in a preferred content expression
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doesn't make git-annex consider those unused keys. So when git-annex is
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only checking preferred content expressions against files in the
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repository (which are obviously used), `unused` in a preferred
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content expression won't match anything.
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becomes
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So when is `unused` useful in a preferred content expression?
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metadata=tag=done
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1. Using `git annex sync --content --all` will operate on all files,
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including unused ones, and take `unused` in preferred content expressions
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into account.
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2. The git-annex assistant periodically scans for unused files, and
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moves them to some repository whose preferred content expression
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matches "unused". (Or, if annex.expireunused is set, it may just delete
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them.)
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### difference: unused
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* `anything`
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The --unused option makes git-annex operate on every key that `git annex
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unused` has determined to be unused. The corresponding `unused` keyword
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in a preferred content expression also matches those keys.
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Matches any version of any file.
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However, using `unused` in a preferred content expression
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doesn't make git-annex consider those keys. So when git-annex is
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only checking preferred content expressions against files in the
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repository (which are obviously used), `unused` in a preferred
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content expression won't match anything.
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* `not expression`
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So when is `unused` useful in a preferred content expression?
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Inverts what the expression matches. For example, `not include=archive/*`
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is the same as `exclude=archive/*`
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* The git-annex assistant periodically scans for unused files, and
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moves them to some repository whose preferred content expression
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matches "unused". (Or, if annex.expireunused is set, it may just delete
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them.)
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* Using `git annex sync --content --all` will operate on all files,
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including unused ones, and take `unused` in preferred content expressions
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into account.
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* `and` / `or` / `( expression )`
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### difference: anything
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The "anything" keyword can be used in a preferred content expression
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to match any version of any file.
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These can be used to build up more complicated expressions.
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## upgrades
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