Skip missing GitHub assets and treat short reads as transient

internal/provider/alpine/github.go

@@ -601,7 +601,7 @@ func pkginfoFromPrefix(prefix []byte) (meta *provider.AlpineMetadata, complete b
 }
 
 // rangeGet returns the first n bytes of downloadURL. full is true when the
-// response body was shorter than n (i.e. we already have the whole object).
+// response holds the whole object.
 func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, downloadURL string, n int64) ([]byte, bool, error) {
 	req, err := http.NewRequestWithContext(ctx, http.MethodGet, downloadURL, nil)
 	if err != nil {
@@ -623,15 +623,9 @@ func (p *GitHubProvider) rangeGet(ctx context.Context, remote models.Remote, dow
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusPartialContent {
-		return nil, false, fmt.Errorf("range GET %s: status %d", downloadURL, resp.StatusCode)
+		return nil, false, fmt.Errorf("range GET: %w", provider.AssetStatusError(downloadURL, resp))
 	}
-
-	body, err := io.ReadAll(io.LimitReader(resp.Body, n))
-	if err != nil {
-		return nil, false, err
-	}
-	full := int64(len(body)) < n
-	return body, full, nil
+	return provider.ReadPrefix(resp, n)
 }
 
 // assetPath is the package's location relative to github.com — the path the