I've got a git repository with plenty of commits that are under no particular branch, I can git show them but when I try to list branches that contain them, it reports back nothing:

I thought this is the dangling commits/tree issue (as a result of -D branch), so I pruned the repo, but I still see the case after that:

$ git fetch origin

$ git fsck --unreachable
$ git fsck

No output, nothing dangling (right?)

$ git show 793db7f272ba4bbdd1e32f14410a52a412667042
commit 793db7f272ba4bbdd1e32f14410a52a412667042
Author: ..

But

$ git branch --contains 793db7f272ba4bbdd1e32f14410a52a412667042

Gives no output

What exactly is the state of that commit? How can I list all commits with similar state, How can I delete commits like those?