Check if depencies are installed

[Geronymos]

Problem

The porgramm breaks if git or highlight are not installed.

highlight also has different versions on different distros, so not all arguments work for all distros (for example highlight --syntax-by-name="$filename" ).

Solution

which highlight || exit
# or better
... | (highlight -... || cat) | ...

The first one just exists the programm and might print an error message. The second one tries to skip the program.