importtree=yes remotes are untrusted, because something is modifying that
remote other than git-annex, and it could change a file at any time, so
git-annex can't rely on the file being there. However, it's possible the user
has a policy of not letting files on the remote be modified. It may even be
that some remotes use storage that avoids such problems. So, there should be
some way to override the default trust level for such remotes.

Currently:

	joey@darkstar:/tmp/y8>git annex semitrust borg
	semitrust borg 
	  This remote's trust level is overridden to untrusted.

The borg special remote is one example of one where it's easy for the user to
decide they're going to not delete old archives from it, and so want git-annex
to trust it.

Below is some docs I wrote for the borg special remote page, should be
moved there when this gets fixed. --[[Joey]]

> There is Remote.appendonly, which prevents making import remotes
> untrusted. So if there were a way to set that for borg, it could
> be configured at initremote/enableremote time. But,
> Remote.Helper.ExportImport also assumes appendonly means that content can
> be accessed by Key, rather than by ImportLocation, which does not work
> for borg.

>> [[done]] via Remote.untrustworthy --[[Joey]]
