fix: do not overwrite whole file

src/main.rs

@@ -1,7 +1,7 @@
 use std::{
     env,
     fmt::Write,
-    fs::{self, File},
+    fs::{self, File, OpenOptions},
     io::{self, BufRead, BufReader},
 };
 
@@ -219,7 +219,9 @@ async fn main() -> Result<()> {
             get_diff(pr, &opts.path, &client).await?;
             let pr = get_pr(pr, &client).await?;
             let title = pr.title.replace("\n", "//");
-            fs::write(&opts.pr_file, format!("{} # {}", pr.number, title))?;
+            let mut file = OpenOptions::new().append(true).open(&opts.pr_file)?;
+            use std::io::Write;
+            writeln!(file, "{} # {}", pr.number, title)?;
         }
     };
     Ok(())