Make --append and --overwrite in conflict with each other

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## 3.0.0 (wip)
 
 * Full rewrite in Rust
+* Use of `--append` and `--overwrite` together gives returns error now
 
 ## 2.4.0 (2023-10-23)
 

src/main.rs

@@ -33,7 +33,7 @@ enum Commands {
         raw: bool,
 
         /// Overwrite target file if it already exists
-        #[arg(long)]
+        #[arg(long, conflicts_with = "append")]
         overwrite: bool,
 
         /// Command to record