Generate cacheable key for CI depending on versioned files diff

generate.sh

#!/bin/sh

a="$(git diff master... --numstat | awk 'NF==3 {total+=$1+$2} END {printf("%d\n", total)}')" \

if [ "$a" -gt 100 ]
then
  echo "bust $(date +%s)" > gitdiff
else
  echo "keep" > gitdiff
fi

Some parameters:
100 - describes number of lines changed threshold.
gitdiff - filepath for partial key, editable
bust/keep - editable

Usage example:

  terser_cache_key: &terser_cache_key v1-webpack_terser-{{ checksum "gitdiff" }}
  terser_cache_key_backup: &terser_cache_key_backup v1-webpack_terser-

  restore_terser_cache: &restore_terser_cache
    run:
      name: Generate partial key for terser-cache
      command: |
        #!/bin/sh

        a="$(git diff master... --numstat | awk 'NF==3 {total+=$1+$2} END {printf("%d\n", total)}')" \

        if [ "$a" -gt 100 ]
        then
          echo "bust $(date +%s)" > gitdiff
        else
          echo "keep" > gitdiff
        fi
    restore_cache:
      name: Restoring Cache (/tmp/terser)
      keys:
        - *terser_cache_key
        - *terser_cache_key_backup