bug#41766: Make it possible to change regexp to identify and highlight grep matches via customization

[Simon Lang]

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.

0001-Make-regexp-used-to-highlight-grep-matches-customiza.patch
Description: 0001-Make-regexp-used-to-highlight-grep-matches-customiza.patch