I've been planning to use git-annex to manage a collection of DVD-Rs (of photos and the like), something along these lines, and especially this paragraph therein:

If the [media is] not rewritable [which in my case it won't be; see below], I might try making the git-annex repo in a temporary directory on the hard disk, and then generating the ISO from that once I've filled it up. Should work fine, I might set "remote..annex-readonly" to true in git repos that had such a disk as a remote to let git-annex know to not try to write to it.

But then there's this bug report: read-only filesystem on remote prevents auto-upgrade from v3 to v5, and prevents using a remote, and Joey's comment:

From a code complication POV, it's useful for git-annex to only support one version of repository at a time.

My concept depends on being able to restore files from my archive, N years and M git-annex versions later, using git annex get (after git annex whereis or the like to find out which volume to mount). If I can't count on the get to work -- and indeed, can pretty much count on it not to, after the next format-version bump -- this whole scheme sounds like a nonstarter.

As far as backwards compatablity goes, I don't anticipate ever removing the upgrade code from git-annex.

This is an archive; therefore it will use write-once media -- if it were rewritable, it would be clobberable should something (including git-annex upgrade!) go wrong.

So, is there a way around this? Or am I (and others) out of luck on using git-annex to manage long-term archival storage?