When changing grep-command or grep-find-command to e.g. ripgrep matches are not highlighted in the grep buffer. This patches makes the regexp that is used to identify matches customizable and hence possible to adapt it to potential grep replacements.

For example:

change  grep command to 

"rg -n -H -S --no-heading --color always -e "

and grep-match-regexp to

"\033\\[[0-9]*m\033\\[[0-9]*1m\033\\[[0-9]*1m\\(.*?\\)\033\\[[0-9]*0m"

to get correct highlighting with ripgrep.