fix(patch_set): accept CRLF line endings in git extended headers

GitHeader::parse extracts header values (file modes, rename/copy
paths, the diff --git line) via strip_line_ending, which stripped
only the trailing \n. In a patch file saved with CRLF line endings
(e.g. on Windows) every extracted value therefore kept its trailing
\r, and parsing a mode header failed outright:

    error parsing patches at byte 0: invalid file mode: 100644\r

Strip a trailing \r as well, mirroring how GNU patch strips trailing
CRs from CRLF patches (the behavior the TODO on strip_line_ending
already pointed at). This only affects git extended header lines;
hunk content is handled by the patch parser itself.

Downstream report: pnpm/pnpm#16641, where a CRLF patch file that
creates a new file fails with ERR_PNPM_INVALID_PATCH on pnpm 12
(pnpm parses patches with diffy's PatchSet::parse).

Tests: crlf_new_file_with_content and crlf_mode_only_change fail on
the unpatched parser with InvalidFileMode("100644\r") and pass with
this change; the full suite (131 lib tests) passes.

Author: Kshot3000

src/patch_set/parse.rs

@@ -821,12 +821,17 @@ fn extract_file_op_unidiff<'a, T: Text + ?Sized>(
     }
 }
 
-/// Strips the trailing `\n` from a line yielded by [`Text::lines`].
+/// Strips the trailing line ending from a line yielded by [`Text::lines`].
 ///
 /// [`Text::lines`] includes line endings; strip for matching.
 fn strip_line_ending<T: Text + ?Sized>(line: &T) -> &T {
-    // TODO: GNU patch strips trailing CRs from CRLF patches automatically.
-    // We should consider adding compat tests for GNU patch.
-    // And `git apply` seems to reject. Worth adding tests as well.
-    line.strip_suffix("\n").unwrap_or(line)
+    // GNU patch strips trailing CRs from CRLF patches automatically.
+    // Mirror that for header lines so a patch file saved with CRLF line
+    // endings (e.g. on Windows) parses the same as its LF equivalent:
+    // without this, extracted values such as the file mode keep their
+    // trailing `\r` and fail to parse (`invalid file mode: 100644\r`).
+    // Note `git apply` seems to reject CRLF patches. Worth adding tests
+    // for both behaviors as well.
+    let line = line.strip_suffix("\n").unwrap_or(line);
+    line.strip_suffix("\r").unwrap_or(line)
 }

src/patch_set/tests.rs

@@ -759,6 +759,54 @@ index 0000000..abc1234
         );
     }
 
+    /// New file with content, with CRLF line endings throughout (e.g. a
+    /// patch file saved on Windows). The extended header values must not
+    /// keep the trailing `\r`: `new file mode 100644\r` previously failed
+    /// with `invalid file mode: 100644\r`.
+    #[test]
+    fn crlf_new_file_with_content() {
+        let input = "\
+diff --git a/new.rs b/new.rs
+new file mode 100644
+index 0000000..abc1234
+--- /dev/null
++++ b/new.rs
+@@ -0,0 +1 @@
++hello
+"
+        .replace('\n', "\r\n");
+        let patches = parse_gitdiff(&input);
+        assert_eq!(patches.len(), 1);
+        assert!(patches[0].operation().is_create());
+        assert_eq!(
+            patches[0].new_mode(),
+            Some(&super::super::FileMode::Regular),
+        );
+    }
+
+    /// Mode-only change with CRLF line endings: both `old mode` and
+    /// `new mode` values must parse despite the trailing `\r`.
+    #[test]
+    fn crlf_mode_only_change() {
+        let input = "\
+diff --git a/script.sh b/script.sh
+old mode 100644
+new mode 100755
+"
+        .replace('\n', "\r\n");
+        let patches = parse_gitdiff(&input);
+        assert_eq!(patches.len(), 1);
+        assert!(patches[0].operation().is_modify());
+        assert_eq!(
+            patches[0].old_mode(),
+            Some(&super::super::FileMode::Regular),
+        );
+        assert_eq!(
+            patches[0].new_mode(),
+            Some(&super::super::FileMode::Executable),
+        );
+    }
+
     /// `diff --git` line with no-prefix paths (`git diff --no-prefix`).
     /// Fallback path parsing works when ---/+++ are absent.
     #[test]