get_maintainer: add test for file in VCS

It's somewhat common for me to ask get_maintainer to tell me who maintains
a patch file rather than the files modified by the patch.

Emit a warning if using get_maintainer.pl -f <patchfile>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lkml.kernel.org/r/f63229c051567041819f25e76f49d83c6e4c0f71.camel@perches.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/get_maintainer.pl

@@ -541,6 +541,9 @@ foreach my $file (@ARGV) {
 	    die "$P: file '${file}' not found\n";
 	}
     }
+    if ($from_filename && (vcs_exists() && !vcs_file_exists($file))) {
+	warn "$P: file '$file' not found in version control $!\n";
+    }
     if ($from_filename || ($file ne "&STDIN" && vcs_file_exists($file))) {
 	$file =~ s/^\Q${cur_path}\E//;	#strip any absolute path
 	$file =~ s/^\Q${lk_path}\E//;	#or the path to the lk tree