I want to watch all directories that contain source files of my app. I don't want to type -w DIR for every directory. xargs can't do this.

I'd like an option that will cause watchexec to take all watch paths from a file, one per line, just like grep -f or rsync --files-form. No need to type watchexec -w if you have the list of directories in a file.

xargs can't do this because the option -w has to be specified many times, once for each directory. The -I flag causes each command to be run with just one arg.

This works, but is not nice (Fish shell)

eval watchexec $(cat my_deps | sed -e 's/^/-w /' | sed ':a;N;s/\n/ /;ba') -- overmind restart app

I guess --watch-file would make sense, given that there's --filter/--filter-file and --ignore/--ignore-file.
As a short option, possibly -F, but I don't think a short option is needed, because this is mostly useful for automation, i.e. scripts.