get_maintainer.pl: reduce need for command-line option -f

If a vcs is used, look to see if the vcs tracks the file specified and
so the -f option becomes optional.

Link: http://lkml.kernel.org/r/7c86a8df0d48770c45778a43b6b3e4627b2a90ee.1469746395.git.joe@perches.com
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/get_maintainer.pl

@@ -133,6 +133,7 @@
     "author_pattern" => "^GitAuthor: (.*)",
     "subject_pattern" => "^GitSubject: (.*)",
     "stat_pattern" => "^(\\d+)\\t(\\d+)\\t\$file\$",
+    "file_exists_cmd" => "git ls-files \$file",
 );
 
 my %VCS_cmds_hg = (
@@ -161,6 +162,7 @@
     "author_pattern" => "^HgAuthor: (.*)",
     "subject_pattern" => "^HgSubject: (.*)",
     "stat_pattern" => "^(\\d+)\t(\\d+)\t\$file\$",
+    "file_exists_cmd" => "hg files \$file",
 );
 
 my $conf = which_conf(".get_maintainer.conf");
@@ -430,7 +432,7 @@ sub read_mailmap {
 	    die "$P: file '${file}' not found\n";
 	}
     }
-    if ($from_filename) {
+    if ($from_filename || vcs_file_exists($file)) {
 	$file =~ s/^\Q${cur_path}\E//;	#strip any absolute path
 	$file =~ s/^\Q${lk_path}\E//;	#or the path to the lk tree
 	push(@files, $file);
@@ -2124,6 +2126,22 @@ sub vcs_file_blame {
     }
 }
 
+sub vcs_file_exists {
+    my ($file) = @_;
+
+    my $exists;
+
+    my $vcs_used = vcs_exists();
+    return 0 if (!$vcs_used);
+
+    my $cmd = $VCS_cmds{"file_exists_cmd"};
+    $cmd =~ s/(\$\w+)/$1/eeg;		# interpolate $cmd
+
+    $exists = &{$VCS_cmds{"execute_cmd"}}($cmd);
+
+    return $exists;
+}
+
 sub uniq {
     my (@parms) = @_;