--all would make git-annex operate on either every key with content present (or in some cases like get and copy --from on every keys with content not present).

This would be useful when a repository has a history with deleted files whose content you want to keep (so you're not using dropunused). Or when you have a lot of branches and just want to be able to fsck every file referenced in any branch (or indeed, any file referenced in any ref). It could also be useful (or even a good default) in a bare repository.

A problem with the idea is that .gitattributes values for keys not currently in the tree would not be available (without horrific anounts of grubbing thru history to find where/when the key used to exist). So numcopies set via .gitattributes would not work. This would be a particular problem for drop and for --auto.

--Joey