The conversion from SVN to git generated a lot of documentation, notes, etc.
The 'cleanest' summary of the process that worked is archived on the following google doc:
https://docs.google.com/document/d/1SFBt7YT0yZ7o2BD4_3CEhKNK_ZfGDCrhR9gr-EoAFcM/edit?ts=5c61c1a4#
There is a document from 2016 when we were discussing it:
There is a document for all the failures:
One tool that was partucularly useful for removing specific files, large files, etc (from the local repo before it got pushed to GitHub) was