[PATCH] checkpatch: Require commit text and warn on long commit text lines

[Prakruthi Deepak Heragu <pheragu@codeaurora.org>]

Commit text is almost always necessary to explain why a change is needed.
Also, warn on commit text lines longer than 75 characters. The commit text
are indented and may wrap on a terminal if they are longer than 75
characters.

Signed-off-by: David Keitel <dkeitel@codeaurora.org>
Signed-off-by: Prakruthi Deepak Heragu <pheragu@codeaurora.org>
---
 scripts/checkpatch.pl | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 91 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index a9c0550..336a8e5 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -14,6 +14,13 @@ use File::Basename;
 use Cwd 'abs_path';
 use Term::ANSIColor qw(:constants);
 
+use constant BEFORE_SHORTTEXT => 0;
+use constant IN_SHORTTEXT_BLANKLINE => 1;
+use constant IN_SHORTTEXT => 2;
+use constant AFTER_SHORTTEXT => 3;
+use constant CHECK_NEXT_SHORTTEXT => 4;
+use constant SHORTTEXT_LIMIT => 75;
+
 my $P = $0;
 my $D = dirname(abs_path($P));
 
@@ -2227,6 +2234,8 @@ sub process {
 	my $prevrawline="";
 	my $stashline="";
 	my $stashrawline="";
+	my $subjectline="";
+	my $sublinenr="";
 
 	my $length;
 	my $indent;
@@ -2282,6 +2291,9 @@ sub process {
 	my $setup_docs = 0;
 
 	my $camelcase_file_seeded = 0;
+	my $shorttext = BEFORE_SHORTTEXT;
+	my $shorttext_exspc = 0;
+	my $commit_text_present = 0;
 
 	my $checklicenseline = 1;
 
@@ -2487,13 +2499,91 @@ sub process {
 			$checklicenseline = 1;
 			next;
 		}
-
 		$here .= "FILE: $realfile:$realline:" if ($realcnt != 0);
 
 		my $hereline = "$here\n$rawline\n";
 		my $herecurr = "$here\n$rawline\n";
 		my $hereprev = "$here\n$prevrawline\n$rawline\n";
 
+		if ($shorttext != AFTER_SHORTTEXT) {
+			if ($shorttext == IN_SHORTTEXT_BLANKLINE && $line=~/\S/) {
+				# the subject line was just processed,
+				# a blank line must be next
+				$shorttext = IN_SHORTTEXT;
+				# this non-blank line may or may not be commit text -
+				# a warning has been generated so assume it is commit
+				# text and move on
+				$commit_text_present = 1;
+				# fall through and treat this line as IN_SHORTTEXT
+			}
+			if ($shorttext == IN_SHORTTEXT) {
+				if ($line=~/^---/ || $line=~/^diff.*/) {
+					if ($commit_text_present == 0) {
+						WARN("NO_COMMIT_TEXT",
+						     "please add commit text explaining " .
+						     "*why* the change is needed\n" .
+						     $herecurr);
+					}
+					$shorttext = AFTER_SHORTTEXT;
+				} elsif (length($line) > (SHORTTEXT_LIMIT +
+							  $shorttext_exspc)
+					 && $line !~ /^:([0-7]{6}\s){2}
+						      ([[:xdigit:]]+\.*
+						       \s){2}\w+\s\w+/xms) {
+					WARN("LONG_COMMIT_TEXT",
+					     "commit text line over " .
+					     SHORTTEXT_LIMIT .
+					     " characters\n" . $herecurr);
+						$commit_text_present = 1;
+				} elsif ($line=~/^\s*[\x21-\x39\x3b-\x7e]+:/) {
+					# this is a tag, there must be commit
+					# text by now
+					if ($commit_text_present == 0) {
+						WARN("NO_COMMIT_TEXT",
+						     "please add commit text explaining " .
+						     "*why* the change is needed\n" .
+						     $herecurr);
+						# prevent duplicate warnings
+						$commit_text_present = 1;
+					}
+				} elsif ($line=~/\S/) {
+					$commit_text_present = 1;
+				}
+			} elsif ($shorttext == IN_SHORTTEXT_BLANKLINE) {
+				# case of non-blank line in this state handled above
+				$shorttext = IN_SHORTTEXT;
+			} elsif ($shorttext == CHECK_NEXT_SHORTTEXT) {
+# The Subject line doesn't have to be the last header in the patch.
+# Avoid moving to the IN_SHORTTEXT state until clear of all headers.
+# Per RFC5322, continuation lines must be folded, so any left-justified
+# text which looks like a header is definitely a header.
+				if ($line!~/^[\x21-\x39\x3b-\x7e]+:/) {
+					# Every rolled over summary-line leaves
+					# a space at the beginning
+					if ($line !~ /^\s/) {
+						$shorttext = IN_SHORTTEXT;
+						if (length($line) != 0) {
+							$commit_text_present = 1;
+						}
+					}
+				}
+			# The next two cases are BEFORE_SHORTTEXT.
+			} elsif ($line=~/^Subject: \[[^\]]*\] (.*)/) {
+				# This is the subject line. Go to
+				# CHECK_NEXT_SHORTTEXT to wait for the commit
+				# text to show up.
+				$shorttext = CHECK_NEXT_SHORTTEXT;
+				$subjectline = $line;
+				$sublinenr = "#$linenr & ";
+			} elsif ($line=~/^    (.*)/) {
+				# Indented format, this must be the summary
+				# line (i.e. git show). There will be no more
+				# headers so we are now in the shorttext.
+				$shorttext = IN_SHORTTEXT_BLANKLINE;
+				$shorttext_exspc = 4;
+			}
+		}
+
 		$cnt_lines++ if ($realcnt != 0);
 
 # Check if the commit log has what seems like a diff which can confuse patch
-- 
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