Tighten comment-stacked-dashes: flag 2+ lines, not just 3+

sql/README.md

@@ -117,16 +117,16 @@ single-line comments.
 
 ### comment-stacked-dashes
 
-A run of 3 or more consecutive `--` lines must use `/* */` syntax instead.
-Up to 2 consecutive `--` lines is fine — a short remark reads fine as `--`.
+A run of 2 or more consecutive `--` lines must use `/* */` syntax instead
+(or carry an explicit `sql-lint:disable comment-stacked-dashes` exception).
+Only a single `--` line is allowed on its own.
 
 ```sql
 -- Bad: stacked dashes
--- spanning three
+-- spanning two
 -- or more lines
 
--- Good: 2 lines is fine
--- as a short remark
+-- Good: a single short remark
 
 /*
  * Good: block comment

sql/bin/sql-lint

@@ -250,10 +250,10 @@ sub check_stacked_dashes {
     my @out;
     my ($start, $end) = (0, 0);
 
-    # Up to 2 consecutive -- lines is allowed (a short two-line remark reads
-    # fine as --); only 3+ must become a /* */ block.
+    # Only a single -- line is allowed; 2+ consecutive lines must become a
+    # /* */ block (or carry an explicit sql-lint:disable exception).
     my $flush = sub {
-        return unless $start && ($end - $start) >= 2;
+        return unless $start && ($end - $start) >= 1;
         my $n = $end - $start + 1;
         maybe_finding(\@out, $lines, $file, $start, 'comment-stacked-dashes',
             "$n consecutive -- comment lines ($start-$end); use /* */ for multi-line comments");

sql/test/fixtures/comment-stacked-dashes.bad.sql

@@ -1,8 +1,11 @@
--- expect-findings: 2
+-- expect-findings: 3
 -- This is a multi-line comment
 -- written with stacked dash lines.
 -- It should use /* */ instead.
 
 -- This is another
 -- stacked comment
 -- spanning three lines.
+
+-- Even two consecutive lines
+-- are no longer allowed.

sql/test/fixtures/comment-stacked-dashes.good.sql

@@ -2,9 +2,6 @@
 
 -- Another single-line comment, separated by a blank line.
 
--- Two consecutive -- lines are also fine;
--- only a run of 3+ must become a /* */ block.
-
 -- /* this is a line comment, not a block comment opening
 
 --/* no space variant