Wow, I had never thought about that. I've run into issues with minified JavaScript files as well, but never really thought about how much it annoyed me.
To "ignore" super-long lines, we can just use a Unix filter:
ag --color --group <pattern> | cut -c -100
the --color and --group force ag to not change the output just because we're piping the output to something that isn't a tty. The cut command simply clamps all lines at 100 chars; feel free to change this length.
This is pretty long, so we could write a wrapper function or something:
agc() {
ag --color --group $@ | cut -c -100
}
Stick it in your zshrc and you're good to go.