Truncate the feed file before writing

Otherwise, the feed may be overwritten, but if it is shorter, it may
contain some leftover data from a previous run. In that case, the file
will be invalid XML, thereby failing to be parsed.

Signed-off-by: Jacob Kiers <jacob@jacobkiers.net>

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* Truncate feed file before writing, to prevent corruption from leftover data.
 * Ensure the feed file name is part of the self URL. This was still hardcoded to `feed.atom`.
 
 ## [0.2.2] - 2022-12-16

src/main.rs

@@ -203,6 +203,7 @@ fn write_file<P: Into<PathBuf>, D: AsRef<[u8]>>(html_path: P, data: D) -> Result
     let path : PathBuf = html_path.into();
     OpenOptions::new()
         .write(true)
+        .truncate(true)
         .create(true)
         .open(&path)
         .unwrap_or_else(|_| panic!("Could not open file '{}' for writing", &path.display()))