The "upload-pack" (the counterpart of "git fetch") needs to disable
commit-graph when responding to a shallow clone/fetch request, but
the way this was done made Git panic, which has been corrected.

* jk/disable-commit-graph-during-upload-pack:
  upload-pack: disable commit graph more gently for shallow traversal
  commit-graph: bump DIE_ON_LOAD check to actual load-time