Notebook diff - minimap or hide unchanged cells

[matangover]

When viewing git diff for large notebooks, it's impossible to know what changed, since there is no visual indication where a change occurred. One option to solve this is showing a diff minimap like when diffing normal files. Another option is a checkbox to hide unchanged cells, as in the following picture (from Deepnote):

[DonJayamanne]

• NotebookTextDiffEditor.previousChange & NotebookTextDiffEditor.nextChange
  Re-hide hidden cells that were expanded
  (accessible)
• Diff Overview Ruler