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rewrite so it's understandable without knowing about the related command-line options

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Joey Hess 2015-06-16 20:17:17 -04:00
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doc/preferred_content.mdwn
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@ -39,8 +39,8 @@ files that `git annex get --auto` will want to get, and `git annex find
will want to drop.
The expressions are very similar to the matching options documented
on the [[git-annex]] man page. At the command line, you can use those
options in commands like this:
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 -')'
@ -48,12 +48,17 @@ The equivalent preferred content expression looks like this:
include=*.mp3 and (not largerthan=100mb)
So, just remove the dashes, basically. However, there are some differences
from the command line options to keep in mind:
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.
### difference: file matching
## expressions
While --include and --exclude match files relative to the current
* `include=glob` and `exclude=glob`
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.
@ -63,16 +68,11 @@ to not retain those files, like this:
exclude=*/archive/*
### difference: no "in="
* `copies=number`
Preferred content expressions have no direct equivalent to `--in`.
Often, it's best to 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 "copies=transfer:1"
### difference: dropping
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
@ -82,11 +82,72 @@ 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.
### difference: "present"
* `copies=trustlevel:number`
There's a special "present" keyword you can use in a preferred content
expression. This means that content is wanted if it's present,
and not otherwise. This leaves it up to you to use git-annex manually
Matches only files that git-annex believes have the specified number
copies, on remotes with the specified trust level. For example,
`copies=trusted:2`
To match any trust level at or higher than a given level,
use 'trustlevel+'. For example, `--copies=semitrusted+:2`
* `copies=groupname:number`
Matches only files that git-annex believes have the specified number of
copies, on remotes in the specified group. For example,
`copies=archive:2`
Preferred content expressions have no equivilant to the `--in`
option, 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
`copies=transfer:1`
* `lackingcopies=number`
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.
* `approxlackingcopies=number`
Like lackingcopies, but does not look at .gitattributes annex.numcopies
settings. This makes it significantly faster.
* `inbackend=name`
Matches only files whose content is stored using the specified key-value
backend.
* `inallgroup=groupname`
Matches only files that git-annex believes are present in all repositories
in the specified group.
* `smallerthan=size` and `largerthan=size`
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"
* `metadata=field=glob`
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 `metadata=tag=done`
To match author metadata, use `metadata=author=* Smith"
* `present`
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:
@ -96,19 +157,17 @@ Note that `not present` is 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..
### difference: "inpreferreddir"
* `inpreferreddir`
There's a special "inpreferreddir" keyword you can use in a
preferred content expression of a special remote. This means that the
content is preferred if it's in a directory (located anywhere in the tree)
with a special name.
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.)
### difference: "standard"
* `standard`
git-annex comes with some built-in preferred content expressions, that
can be used with repositories that are in some [[standard_groups]].
@ -121,9 +180,9 @@ 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/*`"
`standard or include=otherdir/*`
### difference: "groupwanted"
* `groupwanted`
The "groupwanted" keyword can be used to refer to a preferred content
expression that is associated with a group. This is like the "standard"
@ -158,42 +217,39 @@ wants to contain 3 copies of each file:
git annex wanted $repo groupwanted
done
### difference: metadata matching
* `unused`
This:
Matches only keys that `git annex unused` has determined to be unused.
git annex get --metadata tag=done
becomes
metadata=tag=done
### difference: unused
The --unused option makes git-annex operate on every key that `git annex
unused` has determined to be unused. The corresponding `unused` keyword
in a preferred content expression also matches those keys.
However, using `unused` in a preferred content expression
doesn't make git-annex consider those keys. So when git-annex is
This is related the the --unused option.
However, putting `unused` in 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), `unused` in a preferred
content expression won't match anything.
So when is `unused` useful in a preferred content expression?
* The git-annex assistant periodically scans for unused files, and
1. Using `git annex sync --content --all` will operate on all files,
including unused ones, and take `unused` in preferred content expressions
into account.
2. The git-annex assistant periodically scans for unused files, and
moves them to some repository whose preferred content expression
matches "unused". (Or, if annex.expireunused is set, it may just delete
them.)
* Using `git annex sync --content --all` will operate on all files,
including unused ones, and take `unused` in preferred content expressions
into account.
### difference: anything
* `anything`
The "anything" keyword can be used in a preferred content expression
to match any version of any file.
Matches any version of any file.
* `not expression`
Inverts what the expression matches. For example, `not include=archive/*`
is the same as `exclude=archive/*`
* `and` / `or` / `( expression )`
These can be used to build up more complicated expressions.
## upgrades