Ensure that blank lines in multiline strings are shown as changed

Fixes #121

CHANGELOG.md

@@ -18,6 +18,9 @@ would be excluded from context.
 Fixed an issue where lines containing only whitespace would be
 highlighted in purple.
 
+Fixed an issue with changed multiline strings where blank lines were
+not highlighted.
+
 Improved Clojure syntax highlighting.
 
 ### Parsing

sample_files/compare.expected

@@ -67,6 +67,9 @@ sample_files/modules_before.ml sample_files/modules_after.ml
 sample_files/multibyte_before.py sample_files/multibyte_after.py
 8a5e31775d5e788e9158bd4a36e03254  -
 
+sample_files/multiline_string_before.ml sample_files/multiline_string_after.ml
+368850e1e2c9ba6c8bf0b025839769c5  -
+
 sample_files/nest_before.rs sample_files/nest_after.rs
 c36f2f545abee17589e2c18693ad5793  -
 

sample_files/multiline_string_after.ml

@@ -0,0 +1,6 @@
+let x =
+  "
+foo
+
+novel
+"

sample_files/multiline_string_before.ml

@@ -0,0 +1,6 @@
+let x =
+  "
+foo
+
+bar
+"

src/syntax.rs

@@ -737,8 +737,8 @@ impl MatchedPos {
             // Don't create a MatchedPos for empty positions. This
             // occurs when we have lists with empty open/close
             // delimiter positions, such as the top-level list of syntax items.
-            if line_pos.start_col == line_pos.end_col {
-                continue;
+            if pos.len() == 1 && line_pos.start_col == line_pos.end_col {
+                break;
             }
 
             res.push(Self {