checkpatch: fix use via symlink, make missing spelling file non-fatal

Commit 66b47b4a ("checkpatch: look for common misspellings") made it
difficult to use checkpatch via a symlink.

Fix that and make a missing spelling.txt file non-fatal.  Emit a warning
when the spelling.txt file can not be opened.

Reference: http://xkcd.com/1172/Signed-off-by: Joe Perches <joe@perches.com>
Reported-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -7,10 +7,11 @@
 
 use strict;
 use POSIX;
+use File::Basename;
+use Cwd 'abs_path';
 
 my $P = $0;
-$P =~ s@(.*)/@@g;
-my $D = $1;
+my $D = dirname(abs_path($P));
 
 my $V = '0.32';
 
@@ -438,26 +439,29 @@ our $allowed_asm_includes = qr{(?x:
 
 # Load common spelling mistakes and build regular expression list.
 my $misspellings;
-my @spelling_list;
 my %spelling_fix;
-open(my $spelling, '<', $spelling_file)
-    or die "$P: Can't open $spelling_file for reading: $!\n";
-while (<$spelling>) {
-	my $line = $_;
 
-	$line =~ s/\s*\n?$//g;
-	$line =~ s/^\s*//g;
+if (open(my $spelling, '<', $spelling_file)) {
+	my @spelling_list;
+	while (<$spelling>) {
+		my $line = $_;
 
-	next if ($line =~ m/^\s*#/);
-	next if ($line =~ m/^\s*$/);
+		$line =~ s/\s*\n?$//g;
+		$line =~ s/^\s*//g;
 
-	my ($suspect, $fix) = split(/\|\|/, $line);
+		next if ($line =~ m/^\s*#/);
+		next if ($line =~ m/^\s*$/);
+
+		my ($suspect, $fix) = split(/\|\|/, $line);
 
-	push(@spelling_list, $suspect);
-	$spelling_fix{$suspect} = $fix;
+		push(@spelling_list, $suspect);
+		$spelling_fix{$suspect} = $fix;
+	}
+	close($spelling);
+	$misspellings = join("|", @spelling_list);
+} else {
+	warn "No typos will be found - file '$spelling_file': $!\n";
 }
-close($spelling);
-$misspellings = join("|", @spelling_list);
 
 sub build_types {
 	my $mods = "(?x:  \n" . join("|\n  ", @modifierList) . "\n)";
@@ -2246,7 +2250,7 @@ sub process {
 		}
 
 # Check for various typo / spelling mistakes
-		if ($in_commit_log || $line =~ /^\+/) {
+		if (defined($misspellings) && ($in_commit_log || $line =~ /^\+/)) {
 			while ($rawline =~ /(?:^|[^a-z@])($misspellings)(?:$|[^a-z@])/gi) {
 				my $typo = $1;
 				my $typo_fix = $spelling_fix{lc($typo)};