man git-log

里边有写：

−L <start>,<end>:<file>, −L :<funcname>:<file>

Trace the evolution of the line range given by "<start>,<end>" (or the function name regex <funcname>) within the <file>. You may not give any pathspec limiters. This is currently limited to a walk starting from a single revision, i.e., you may only give zero or one positive revision arguments. You can specify this option more than once.