https://github.com/beautifier/js-beautify can be used to format Smarty template files *.tpl
smarty-php/smarty#1136 (comment)
Investigate using this to format the files and add it to the CI system.
An initial example command:
find tpl -type f -iname '*.tpl' -print0 \
| xargs --null js-beautify --type html --templating smarty --indent-size 4 --replace --eol '\n' --end-with-newline