checkpatch: add new warnings to author signoff checks.

The author signed-off-by checks are currently very vague. Cases like same
name or same address are not handled separately.

For example, running checkpatch on commit be6577af0cef ("parisc: Add
atomic64_set_release() define to avoid CPU soft lockups"), gives:

WARNING: Missing Signed-off-by: line by nominal patch author
'John David Anglin <[e-mail]>'

The signoff line was:
"Signed-off-by: Dave Anglin <[e-mail]>"

Clearly the author has signed off but with a slightly different version
of his name. A more appropriate warning would have been to point out
at the name mismatch instead.

Previously, the values assumed by $authorsignoff were either 0 or 1
to indicate whether a proper sign off by author is present.
Extended the checks to handle four new cases.

$authorsignoff values now denote the following:

0: Missing sign off by patch author.

1: Sign off present and identical.

2: Addresses and names match, but comments differ.
"James Watson(JW) <[e-mail]>", "James Watson <[e-mail]>"

3: Addresses match, but names are different.
"James Watson <[e-mail]>", "James <[e-mail]>"

4: Names match, but addresses are different.
"James Watson <[e-mail]>", "James Watson <[e-mail]>"

5: Names match, addresses excluding subaddress details (RFC 5233) match.
"James Watson <[e-mail]>", "James Watson <[e-mail]>"

Also introduced a new message type FROM_SIGN_OFF_MISMATCH
for cases 2, 3, 4 and 5.

Suggested-by: Joe Perches <[e-mail]>
Signed-off-by: Dwaipayan Ray <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Acked-by: Joe Perches <[e-mail]>
Link: https://lore.kernel.org/linux-kernel-mentees/[e-mail]/
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

scripts/checkpatch.pl

···
 		}
 	}
 
+	$comment = trim($comment);
 	$name = trim($name);
 	$name =~ s/^\"|\"$//g;
-	$name =~ s/(\s*\([^\)]+\))\s*//;
-	if (defined($1)) {
+	if ($name =~ s/(\s*\([^\)]+\))\s*//) {
 		$name_comment = trim($1);
 	}
 	$address = trim($address);
···
 }
 
 sub format_email {
-	my ($name, $address) = @_;
+	my ($name, $name_comment, $address, $comment) = @_;
 
 	my $formatted_email;
 
+	$name_comment = trim($name_comment);
+	$comment = trim($comment);
 	$name = trim($name);
 	$name =~ s/^\"|\"$//g;
 	$address = trim($address);
···
 	if ("$name" eq "") {
 		$formatted_email = "$address";
 	} else {
-		$formatted_email = "$name <$address>";
+		$formatted_email = "$name$name_comment <$address>";
 	}
-
+	$formatted_email .= "$comment";
 	return $formatted_email;
 }
 
···
 	my ($email) = @_;
 
 	my ($email_name, $name_comment, $email_address, $comment) = parse_email($email);
-	return format_email($email_name, $email_address);
+	return format_email($email_name, $name_comment, $email_address, $comment);
 }
 
 sub same_email_addresses {
-	my ($email1, $email2) = @_;
+	my ($email1, $email2, $match_comment) = @_;
 
 	my ($email1_name, $name1_comment, $email1_address, $comment1) = parse_email($email1);
 	my ($email2_name, $name2_comment, $email2_address, $comment2) = parse_email($email2);
 
+	if ($match_comment != 1) {
+		return $email1_name eq $email2_name &&
+		       $email1_address eq $email2_address;
+	}
 	return $email1_name eq $email2_name &&
-	       $email1_address eq $email2_address;
+	       $email1_address eq $email2_address &&
+	       $name1_comment eq $name2_comment &&
+	       $comment1 eq $comment2;
 }
 
 sub which {
···
 	my $signoff = 0;
 	my $author = '';
 	my $authorsignoff = 0;
+	my $author_sob = '';
 	my $is_patch = 0;
 	my $is_binding_patch = -1;
 	my $in_header_lines = $file ? 0 : 1;
···
 		if ($line =~ /^\s*signed-off-by:\s*(.*)/i) {
 			$signoff++;
 			$in_commit_log = 0;
-			if ($author ne '') {
-				if (same_email_addresses($1, $author)) {
+			if ($author ne ''  && $authorsignoff != 1) {
+				if (same_email_addresses($1, $author, 1)) {
 					$authorsignoff = 1;
+				} else {
+					my $ctx = $1;
+					my ($email_name, $email_comment, $email_address, $comment1) = parse_email($ctx);
+					my ($author_name, $author_comment, $author_address, $comment2) = parse_email($author);
+
+					if ($email_address eq $author_address && $email_name eq $author_name) {
+						$author_sob = $ctx;
+						$authorsignoff = 2;
+					} elsif ($email_address eq $author_address) {
+						$author_sob = $ctx;
+						$authorsignoff = 3;
+					} elsif ($email_name eq $author_name) {
+						$author_sob = $ctx;
+						$authorsignoff = 4;
+
+						my $address1 = $email_address;
+						my $address2 = $author_address;
+
+						if ($address1 =~ /(\S+)\+\S+(\@.*)/) {
+							$address1 = "$1$2";
+						}
+						if ($address2 =~ /(\S+)\+\S+(\@.*)/) {
+							$address2 = "$1$2";
+						}
+						if ($address1 eq $address2) {
+							$authorsignoff = 5;
+						}
+					}
 				}
 			}
 		}
···
 			}
 
 			my ($email_name, $name_comment, $email_address, $comment) = parse_email($email);
-			my $suggested_email = format_email(($email_name, $email_address));
+			my $suggested_email = format_email(($email_name, $name_comment, $email_address, $comment));
 			if ($suggested_email eq "") {
 				ERROR("BAD_SIGN_OFF",
 				      "Unrecognized email address: '$email'\n" . $herecurr);
···
 				$dequoted =~ s/" </ </;
 				# Don't force email to have quotes
 				# Allow just an angle bracketed address
-				if (!same_email_addresses($email, $suggested_email)) {
+				if (!same_email_addresses($email, $suggested_email, 0)) {
 					WARN("BAD_SIGN_OFF",
-					     "email address '$email' might be better as '$suggested_email$comment'\n" . $herecurr);
+					     "email address '$email' might be better as '$suggested_email'\n" . $herecurr);
 				}
 			}
 
···
 		if ($signoff == 0) {
 			ERROR("MISSING_SIGN_OFF",
 			      "Missing Signed-off-by: line(s)\n");
-		} elsif (!$authorsignoff) {
-			WARN("NO_AUTHOR_SIGN_OFF",
-			     "Missing Signed-off-by: line by nominal patch author '$author'\n");
+		} elsif ($authorsignoff != 1) {
+			# authorsignoff values:
+			# 0 -> missing sign off
+			# 1 -> sign off identical
+			# 2 -> names and addresses match, comments mismatch
+			# 3 -> addresses match, names different
+			# 4 -> names match, addresses different
+			# 5 -> names match, addresses excluding subaddress details (refer RFC 5233) match
+
+			my $sob_msg = "'From: $author' != 'Signed-off-by: $author_sob'";
+
+			if ($authorsignoff == 0) {
+				ERROR("NO_AUTHOR_SIGN_OFF",
+				      "Missing Signed-off-by: line by nominal patch author '$author'\n");
+			} elsif ($authorsignoff == 2) {
+				CHK("FROM_SIGN_OFF_MISMATCH",
+				    "From:/Signed-off-by: email comments mismatch: $sob_msg\n");
+			} elsif ($authorsignoff == 3) {
+				WARN("FROM_SIGN_OFF_MISMATCH",
+				     "From:/Signed-off-by: email name mismatch: $sob_msg\n");
+			} elsif ($authorsignoff == 4) {
+				WARN("FROM_SIGN_OFF_MISMATCH",
+				     "From:/Signed-off-by: email address mismatch: $sob_msg\n");
+			} elsif ($authorsignoff == 5) {
+				WARN("FROM_SIGN_OFF_MISMATCH",
+				     "From:/Signed-off-by: email subaddress mismatch: $sob_msg\n");
+			}
 		}
 	}