scripts/get_maintainer.pl: fix --non with --git-blame and cleanups

Fix email matching without name --n and --git-blame
   Using --non and --git-blame caused maintainer signature
   matching to fail.  Fixed that by adding 3rd argument to
   sub format_email to control show/hide name portion of address
Slurp -f file instead of reading line-by-line for K: pattern matching.
   Suggested by Wolfram Sang as more efficient
Refactor git command execution
   Break into 2 functions, execute/analyze
   Share code between --git and --git-blame
   Don't warn multiple times when git isn't installed
Improve stats reporting
   --git-min-percent and -- rolestats now count the total number of commits
   for either the period of --git-since or if using --git-blame the commits
   used by the current file and calculate commit % as
      # of commits signed / total commits * 100
Code style cleaning
   Use consistent sub foo { my (args...) = @_;

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Greg KH <greg@kroah.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>