rust: don't attempt to upload asset that already exists

This is a better solution.

Author: indygreg

src/github.rs

@@ -245,6 +245,11 @@ pub async fn command_upload_release_distributions(args: &ArgMatches<'_>) -> Resu
     };
 
     for filename in wanted_filenames.intersection(&filenames) {
+        if release.assets.iter().any(|asset| &asset.name == filename) {
+            println!("release asset {} already present; skipping", filename);
+            continue;
+        }
+
         let path = dist_dir.join(filename);
         let file_data = std::fs::read(&path)?;
 
@@ -269,11 +274,6 @@ pub async fn command_upload_release_distributions(args: &ArgMatches<'_>) -> Resu
 
         let response = client.execute(request).await?;
 
-        if response.status() == 422 {
-            println!("HTTP 422 when uploading {}; ignoring", filename);
-            continue;
-        }
-
         if !response.status().is_success() {
             return Err(anyhow!("HTTP {}", response.status()));
         }