correct the '-m' argument for grep. Then regenralize git-extra

'-m' option is supported both in GNU grep and in BSD grep
GNU grep: <http://linux.die.net/man/1/grep>
BSD grep:
<https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/grep.1.html>
correct the format of git-rebase-patch.md. Now we can handle it with script

Also regeneralize all markdown documents.