Normalize "\r\n" to "\n" to ensure ^ and $ match line boundaries

The regex crate only considers "\n" a line boundary, so ^ and $ don't
match "\r\n". This can be a problem if code is checked out on Windows
and Git helpfully rewrites your "\n" to "\r\n". I ran into this
problem when testing GitHub Actions on the textwrap repository.

See rust-lang/regex#244.

Cargo.toml

@@ -29,3 +29,6 @@ toml = "0.5"
 url = "2.0"
 itertools = "0.9"
 regex = "1.1"
+
+[dev-dependencies]
+tempfile = "3.1"

src/contains_regex.rs

@@ -118,4 +118,22 @@ mod tests {
         )
     }
 
+    #[test]
+    fn line_boundaries() {
+        // The regex crate doesn't treat \r\n as a line boundary
+        // (https://github.com/rust-lang/regex/issues/244), so
+        // version-sync makes sure to normalize \r\n to \n when
+        // reading files.
+        use std::io::Write;
+        let mut file = tempfile::NamedTempFile::new().unwrap();
+
+        println!("Path: {}", file.path().to_str().unwrap());
+
+        file.write_all(b"first line\r\nsecond line\r\nthird line\r\n")
+            .unwrap();
+        assert_eq!(
+            check_contains_regex(file.path().to_str().unwrap(), "^second line$", "", ""),
+            Ok(())
+        )
+    }
 }

src/helpers.rs

@@ -9,12 +9,14 @@ use semver_parser::version::Version;
 /// The common result type, our errors will be simple strings.
 pub type Result<T> = result::Result<T, String>;
 
-/// Return all data from `path`.
+/// Return all data from `path`. Line boundaries are normalized from
+/// "\r\n" to "\n" to make sure "^" and "$" will match them. See
+/// https://github.com/rust-lang/regex/issues/244 for details.
 pub fn read_file(path: &str) -> io::Result<String> {
     let mut file = File::open(path)?;
     let mut buf = String::new();
     file.read_to_string(&mut buf)?;
-    Ok(buf)
+    Ok(buf.replace("\r\n", "\n"))
 }
 
 /// Indent every line in text by four spaces.