checkpatch: warn on bare SHA-1 commit IDs in commit logs

Commit IDs should have commit descriptions too.  Warn when a 12 to 40 byte
SHA-1 is used in commit logs.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -2317,9 +2317,11 @@ sub process {
 		}
 
 # Check for git id commit length and improperly formed commit descriptions
-		if ($in_commit_log && $line =~ /\b(c)ommit\s+([0-9a-f]{5,})/i) {
-			my $init_char = $1;
-			my $orig_commit = lc($2);
+		if ($in_commit_log &&
+		    ($line =~ /\bcommit\s+[0-9a-f]{5,}\b/i ||
+		     $line =~ /\b[0-9a-f]{12,40}\b/i)) {
+			my $init_char = "c";
+			my $orig_commit = "";
 			my $short = 1;
 			my $long = 0;
 			my $case = 1;
@@ -2330,6 +2332,13 @@ sub process {
 			my $orig_desc = "commit description";
 			my $description = "";
 
+			if ($line =~ /\b(c)ommit\s+([0-9a-f]{5,})\b/i) {
+				$init_char = $1;
+				$orig_commit = lc($2);
+			} elsif ($line =~ /\b([0-9a-f]{12,40})\b/i) {
+				$orig_commit = lc($1);
+			}
+
 			$short = 0 if ($line =~ /\bcommit\s+[0-9a-f]{12,40}/i);
 			$long = 1 if ($line =~ /\bcommit\s+[0-9a-f]{41,}/i);
 			$space = 0 if ($line =~ /\bcommit [0-9a-f]/i);