find [options here] -exec bash -c 'expand --initial --tabs=4 {} | sponge {}' +
- https://joeyh.name/code/moreutils/. Contains
sponge. expandis in GNU coreutils
find [options here] -exec bash -c 'expand --initial --tabs=4 {} | sponge {}' +
sponge.expand is in GNU coreutils