May be it is already available and thus not really todo (feel welcome to close then or I will), and/or I have asked before, but I failed to find it.  Sorry if duplicating the issue.

In some scenarios we do know ahead of time url + size + filename (thus extension) + corresponding checksum for the content. We would like to implement `addurl` which would not even talk to the remote server but just "mint" corresponding path to the key under `.git/annex/objects` and `registerurl` to it.  But I failed to find a convenience annex command which would allow us to get the full key (accounting for `E` the way git annex does), and full path to it (thus adding `DIRHASH` which special remotes could "query", and which is appropriate given the repository settings).

I made subject prefixed with `calckey`  since it seems like the closest hit but it does need an actual file.

edit1: I was pointed to [forum/Is_it_possible_adding_files_to_git_annex_bypassing___40__some_parts_of__41___the_git_annex_tools/#comment-a80b2371012dda93ad7fb4926af91b48](https://git-annex.branchable.com/forum/Is_it_possible_adding_files_to_git_annex_bypassing___40__some_parts_of__41___the_git_annex_tools/#comment-a80b2371012dda93ad7fb4926af91b48) which seems to be the closest hit, but relies on assuming how extension is extracted by annex, which might be incorrect for some files.

[[!meta author=yoh]]
[[!tag projects/datalad]]

> [[done]] --[[Joey]]
