checkpatch: add fix and improve warning msg for non-standard signature

Currently checkpatch warns for BAD_SIGN_OFF on non-standard signature
styles.

A large number of these warnings occur because of typo mistakes in
signature tags.  An evaluation over v4.13..v5.8 showed that out of 539
warnings due to non-standard signatures, 87 are due to typo mistakes.

Following are the standard signature tags which are often incorrectly
used, along with their individual counts of incorrect use (over
v4.13..v5.8):

 Reviewed-by: 42
 Signed-off-by: 25
 Reported-by: 6
 Acked-by: 4
 Tested-by: 4
 Suggested-by: 4
Provide a fix by calculating levenshtein distance for the signature tag
with all the standard signatures and suggest a fix with a signature, whose
edit distance is less than or equal to 2 with the misspelled signature.

Out of the 86 mispelled signatures fixed with this approach, 85 were found
to be good corrections and 1 was bad correction.

Following was found to be a bad correction:
 Tweeted-by (count: 1) => Tested-by

Link: https://lkml.kernel.org/r/20201128204333.7054-1-yashsri421@gmail.com
Signed-off-by: Aditya Srivastava <yashsri421@gmail.com>
Acked-by: Joe Perches <joe@perches.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 241c064f358bef8a25670e17e47f26ea918039ff..d7616a6f1436b1130ed28e8aa6b87d12ab7367aa 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -506,6 +506,64 @@ our $signature_tags = qr{(?xi:
        Cc:
 )};
 
+sub edit_distance_min {
+       my (@arr) = @_;
+       my $len = scalar @arr;
+       if ((scalar @arr) < 1) {
+               # if underflow, return
+               return;
+       }
+       my $min = $arr[0];
+       for my $i (0 .. ($len-1)) {
+               if ($arr[$i] < $min) {
+                       $min = $arr[$i];
+               }
+       }
+       return $min;
+}
+
+sub get_edit_distance {
+       my ($str1, $str2) = @_;
+       $str1 = lc($str1);
+       $str2 = lc($str2);
+       $str1 =~ s/-//g;
+       $str2 =~ s/-//g;
+       my $len1 = length($str1);
+       my $len2 = length($str2);
+       # two dimensional array storing minimum edit distance
+       my @distance;
+       for my $i (0 .. $len1) {
+               for my $j (0 .. $len2) {
+                       if ($i == 0) {
+                               $distance[$i][$j] = $j;
+                       } elsif ($j == 0) {
+                               $distance[$i][$j] = $i;
+                       } elsif (substr($str1, $i-1, 1) eq substr($str2, $j-1, 1)) {
+                               $distance[$i][$j] = $distance[$i - 1][$j - 1];
+                       } else {
+                               my $dist1 = $distance[$i][$j - 1]; #insert distance
+                               my $dist2 = $distance[$i - 1][$j]; # remove
+                               my $dist3 = $distance[$i - 1][$j - 1]; #replace
+                               $distance[$i][$j] = 1 + edit_distance_min($dist1, $dist2, $dist3);
+                       }
+               }
+       }
+       return $distance[$len1][$len2];
+}
+
+sub find_standard_signature {
+       my ($sign_off) = @_;
+       my @standard_signature_tags = (
+               'Signed-off-by:', 'Co-developed-by:', 'Acked-by:', 'Tested-by:',
+               'Reviewed-by:', 'Reported-by:', 'Suggested-by:'
+       );
+       foreach my $signature (@standard_signature_tags) {
+               return $signature if (get_edit_distance($sign_off, $signature) <= 2);
+       }
+
+       return "";
+}
+
 our @typeListMisordered = (
        qr{char\s+(?:un)?signed},
        qr{int\s+(?:(?:un)?signed\s+)?short\s},
@@ -2773,8 +2831,17 @@ sub process {
                        my $ucfirst_sign_off = ucfirst(lc($sign_off));
 
                        if ($sign_off !~ /$signature_tags/) {
-                               WARN("BAD_SIGN_OFF",
-                                    "Non-standard signature: $sign_off\n" . $herecurr);
+                               my $suggested_signature = find_standard_signature($sign_off);
+                               if ($suggested_signature eq "") {
+                                       WARN("BAD_SIGN_OFF",
+                                            "Non-standard signature: $sign_off\n" . $herecurr);
+                               } else {
+                                       if (WARN("BAD_SIGN_OFF",
+                                                "Non-standard signature: '$sign_off' - perhaps '$suggested_signature'?\n" . $herecurr) &&
+                                           $fix) {
+                                               $fixed[$fixlinenr] =~ s/$sign_off/$suggested_signature/;
+                                       }
+                               }
                        }
                        if (defined $space_before && $space_before ne "") {
                                if (WARN("BAD_SIGN_OFF",