2 ms·

It uses its own. See https://github.com/git/git/blob/master/builtin/grep.c https://github.com/git/git/blob/master/builtin/grep.c

• unwind 14y ago
  That seems to be the "command infrastructure" for the grep builtin. The actual grep engine is in https://github.com/git/git/blob/master/grep.c https://github.com/git/git/blob/master/grep.c.