go get github.com/whatalnk/xlsx2json
go install github.com/whatalnk/xlsx2json

xlsx2json -input=data.xlsx -output=data.xlsx.json

xlsx2json -input=data.xlsx -output=-

xlsx2json -input=data.xlsx.json -output=data.xlsx.json.xlsx

*.xlsx diff=xlsx2json

[diff "xlsx2json"]
  binary = true
  textconv = xlsx2json -input=$1 -output=-