git annex whereused would report where in the git repository a key is used, as a complement to git-annex unused.

Use cases include users not getting confused about why git-annex unused says a key is used.

Also, it could scan through history to find where a key was used. git-annex unused outputs a suggestion to use a rather hairy git log -S command to do that currently.

If it does both these things, it could explain why git-annex unused considers a key used despite a previous git rev referring to it. Eg:

# git annex whereused SHA1--foo
checking index... unused
checking branches... unused
checking tags... unused
checking history... last used in master^40:somefile
checking reflog... last used in HEAD@{30}:somefile

--Joey

First pass is a keys db lookup to filenames.

The historical pass can be done fairly efficiently by using git log -Skey --exclude=*/git-annex --glob=* --exclude=git-annex --remotes=* --tags=* --pretty='%H' --raw and fall back to git log -Skey --walk-reflogs --pretty='%gd' --raw if nothing was found.

That makes git log check all commits reachable from those refs, probably as efficiently as possible, and stop after one match. It won't allow quite as nice a display as above.

Parse the log output for commit sha and filename. Double-check by catting the file's object and making sure it parses as an annex link or pointer.

Then use git describe --contains --all to get a description of the commit sha, which will be something like "master~2" or "origin/master~2", and add ":filename" to get the ref to output.

Or, if it was found in the ref log, take the "HEAD@{n}" from log output, and add ":filename"

done --Joey