Fix crash due to trailing newlines in string nodes at EOF

Fixes #782

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## 0.62 (unreleased)
 
+### Diffing
+
+Improved handling of multiline strings, which could cause a crash if
+they occurred at the end of the file. This was particularly noticeable
+with YAML.
+
 ## 0.61 (released 24th October 2024)
 
 **Recommended git configuration has changed! Please update your

sample_files/compare.expected

@@ -160,6 +160,9 @@ f761255d521267ace4f4887a21664a12  -
 sample_files/multiline_string_1.ml sample_files/multiline_string_2.ml
 ed80815053ba156505d156277d0f4195  -
 
+sample_files/multiline_string_eof_1.yml sample_files/multiline_string_eof_2.yml
+ba8a8e7ed2f4b519feaa391fd05c95fe  -
+
 sample_files/nest_1.rs sample_files/nest_2.rs
 d3a799fe2cd9d81aa251c96af5cd9711  -
 

sample_files/multiline_string_eof_1.yml

@@ -0,0 +1,3 @@
+run: |
+          set -x
+          git clone  https://github.com/torvalds/linux

sample_files/multiline_string_eof_2.yml

@@ -0,0 +1,2 @@
+run: |
+          git clone  https://github.com/torvalds/linux

src/parse/syntax.rs

@@ -258,7 +258,11 @@ impl<'a> Syntax<'a> {
             content = &content[..content.len() - 1];
         }
 
-        if kind == AtomKind::Comment && content.ends_with('\n') {
+        // If a parser adds a trailing newline to the atom, discard
+        // it. It produces worse diffs: we'd rather align on real
+        // content, and complicates handling of trailing newlines at
+        // the end of the file.
+        if content.ends_with('\n') {
             position.pop();
             content = &content[..content.len() - 1];
         }