- `git format-patch --zero-commit` doesn't affect `index xxx...yyy` lines, only `From: `
- so use the _classy_ "use a regex with a callback" solution as git format-patch doesn't offer one
- this will make _all_ patches change when rewritten, but hopefully _for the last time_ !
- we need to preserve `index 000000000000..xxx` as zeros, which indicate new file creation, thus:
- new file creations are rewritten as `index 000000000000..111111111111`
- non-creations are rewritten as `index 111111111111..222222222222`
- this is the final version of #6455
282fb964e5