[PATCH v5] checkpatch: add new exception to repeated word check

[Dwaipayan Ray]

Recently, commit 4f6ad8aa1eac ("checkpatch: move repeated word test")
moved the repeated word test to check for more file types. But after
this, if checkpatch.pl is run on MAINTAINERS, it generates several
new warnings of the type:

WARNING: Possible repeated word: 'git'

For example:
WARNING: Possible repeated word: 'git'
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git

So, the pattern "git git://..." is a false positive in this case.

There are several other combinations which may produce a wrong
warning message, such as "@size size", ":Begin begin", etc.

Extend repeated word check to compare the characters before and
after the word matches.

If there is a non whitespace character before the first word or a
non whitespace character excluding punctuation characters after
the second word, then the check is skipped and the warning is avoided.

Also add case insensitive word matching to the repeated word check.

Link: https://lore.kernel.org/linux-kernel-mentees/81b6a0bb2c7b9256361573f7a13201ebcd4876f1.camel@xxxxxxxxxxx/
Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
Suggested-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
Signed-off-by: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx>
---
 scripts/checkpatch.pl | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index f1a4e61917eb..ec380626bebc 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3052,19 +3052,30 @@ sub process {
 
 # check for repeated words separated by a single space
 		if ($rawline =~ /^\+/ || $in_commit_log) {
+			pos($rawline) = 1 if (!$in_commit_log);
 			while ($rawline =~ /\b($word_pattern) (?=($word_pattern))/g) {
 
 				my $first = $1;
 				my $second = $2;
-
+				my $start_pos = $-[1];
+				my $end_pos = $+[2];
 				if ($first =~ /(?:struct|union|enum)/) {
 					pos($rawline) += length($first) + length($second) + 1;
 					next;
 				}
 
-				next if ($first ne $second);
+				next if (lc($first) ne lc($second));
 				next if ($first eq 'long');
 
+				# check for character before and after the word matches
+				my $start_char = '';
+				my $end_char = '';
+				$start_char = substr($rawline, $start_pos - 1, 1) if ($start_pos > ($in_commit_log ? 0 : 1));
+				$end_char = substr($rawline, $end_pos, 1) if ($end_pos < length($rawline));
+
+				next if ($start_char =~ /^\S$/);
+				next if (index(" \t.,;?!", $end_char) == -1);
+
 				if (WARN("REPEATED_WORD",
 					 "Possible repeated word: '$first'\n" . $herecurr) &&
 				    $fix) {
-- 
2.27.0