git-filter-branch
  Ease of use differences in usability:
    Easier path selection and renaming
    Rewrite sha1sums (and abbreviations) in commit messages
    Defaults to pruning empty commits (but only BECOME empty commits)
      - (Technical notes, on kinds of empty:
         - Empty due to blob filtering resulting in later patch becoming empty
         - Empty due to path filtering
         - Empty branch causing merge to lose parent(s) -- 3 styles
           - One or more parents had no changes themselves or in their history
           - Most recent non-empty commit on all branches was either the
             merge-base or an ancestor (i.e. keeping the merge commit would
             mean merging a commit with itself)
           - Most recent non-empty commit on one parent's side of history is
             an ancestor of another parent (i.e. that side no longer has any
             interesting changes, and the parent corresponding to the empty
             side should be removed)
         - Empty ref due to entire history before it being empty
    Deletes stuff not requested in the rewrite (unless overridden), so that
      it doesn't confuse user or accidentally get re-pushed
    Typically far faster to execute
    Bails if not in a clean clone by default
      - Users have a far easier time restoring if they can just nuke the clone
      - Avoids the default need for users to mess with backups of original refs
        (either for restoration, or for pruning to make sure repo is clean)
    Repacks and shrinks repo for you (unless overridden)
      - Makes it easier to ensure you've cleaned out unwanted stuff

  Advantages over git-repo-filter:
    - Filters every file once per revision even if unmodified between commits;
      allows filtering differently for different commits.
    
    
  
bfg repo-cleaner
  Ease of use differences in usability:
    Automatic repack and shrink repo (instead of documenting extra steps)
    No stupid 'fix your current branch first manually, then run'
    Pathname inclusion, not just exclusion
    Full pathname matching, instead of just *basename* (globs for basename)

  Capability differences:
    Prunes commits which become empty due to filtering
    Lots of general filtering options outside of removing a few big files

  Advantages of BFG repo cleaner:
    - Very focused on just removing crazy big files, and sensitive data
    -