In case anyone else is stuck with this: it just means the write permissions are wrong in the repo that you’re pushing to. Go and
chmod -R it so that the user you’re accessing the git server with has write access.
$ git push vps
Counting objects: 47, done.
Compressing objects: 100% (34/34), done.
Writing objects: 100% (34/34), 5.72 KiB, done.
Total 34 (delta 24), reused 0 (delta 0)
error: unable to write sha1 filename ./objects/74/f54987f7c49320a3c487822d291
19a6477c: Permission denied
fatal: failed to write object
error: unpack failed: unpacker exited with error code
! [remote rejected] groups -> groups (n/a (unpacker error))
! [remote rejected] master -> master (n/a (unpacker error))
error: failed to push some refs to 'ssh://firstname.lastname@example.org:/home/git/todoapp.git'