Listing and deleting Git commits that are under no

Question

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 same behavior after that:

$ git fetch origin

$ git fsck --unreachable
$ git fsck

No output, nothing dangling (right?). But the commit exists

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

and it is not reachable through any branch as

$ git branch --contains 793db7f272ba4bbdd1e32f14410a52a412667042

gives no output.

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

Answer 1

I had a similar issue. I ran git branch --contains <commit>, and it returned no output just like in the question.

But even after running

git reflog expire --expire-unreachable=now --all
git gc --prune=now

my commit was still accessible using git show <commit>. This was because one of the commits in its detached/dangled "branch" was tagged. I removed the tag, ran the above commands again, and I was golden. git show <commit> returned fatal: bad object <commit> - exactly what I needed. Hopefully this helps someone else that was as stuck as I was.