Some remotes are too small to sync everything to them.

The case of a small remote on a gadget that the user interacts with,
such as a phone, where they may want to request it get content
it doesn't currently have, is covered by the [[partial_content]] page.

But often the remote is just a removable drive or a cloud remote,
that has a limited size. This page is about making the assistant do
something smart with such remotes.

## specifying what data belongs on a remote

Imagine a per-remote `annex-accept` setting, that matches things that
should be stored on the remote.

For example, a MP3 player might use:
`smallerthan(10mb) and filename(*.mp3) and (not filename(junk/*))`

Adding that as a filter to files sent to a remote should be
straightforward.

A USB drive that is carried between three laptops and used to sync data
between them might use: `not (in=laptop1 and in=laptop2 and in=laptop3)`

In this case, transferring data from the usb repo should
check if `annex-accept` then rejects the data, and if so, drop it
from the repo. So once all three laptops have the data, it is
pruned from the transfer drive.

It may make sense to have annex-accept info also be stored in the git-annex
branch, for settings that should apply to a repo globally. Does it make
sense to have local configuration too?

## repo classes

Seems like git-annex needs a way to know the classes of repos. Some
classes:

* enduser: The user interacts with this repo directly.
* archival: This repo accumulates stuff, and once it's in enough archives,
  it tends to get removed from other places.
* transfer: This repo is used to transfer data between enduser repos,
  it does not hold data for long periods of time, and tends to have a
  limited size.

Add a class.log that can assign repos to these or other classes.
(Should a repo be allowed to be in multiple classes?)

Some examples of using classes:

* Want to remove content from a repo, if it's not an archival repo,
  and the content has reached at least one archival repo:

  `(not class=archival) and (not copies=archival:1)`

  That would make send to configure on all repos, or even set
  a global `annex.accept` to it.

* Make a cloud repo only hold data until all known clients have a copy:

  `not inall(enduser)`

## configuration

The above is all well and good for those who enjoy boolean algebra, but
how to configure these sorts of expressions in the webapp?