Skip missing GitHub assets and treat short reads as transient

internal/provider/deb/github.go

@@ -574,7 +574,7 @@ func controlFromPrefix(prefix []byte) (control string, complete bool, err error)
 }
 
 // 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 {
@@ -596,15 +596,9 @@ 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)
 }
 
 func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote, downloadURL string) (string, error) {
@@ -627,7 +621,7 @@ func (p *GitHubProvider) computeSHA256(ctx context.Context, remote models.Remote
 	}
 	defer resp.Body.Close()
 	if resp.StatusCode != http.StatusOK {
-		return "", fmt.Errorf("GET %s: status %d", downloadURL, resp.StatusCode)
+		return "", fmt.Errorf("GET: %w", provider.AssetStatusError(downloadURL, resp))
 	}
 
 	h := sha256.New()

internal/provider/deb/github_test.go

@@ -7,6 +7,7 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -468,3 +469,13 @@ func TestGitHubAssetPatternFilter(t *testing.T) {
 		t.Fatalf("pattern filter failed, rows=%+v", rows)
 	}
 }
+
+func TestGitHubDeriveAssetMissingPackageIsInvalid(t *testing.T) {
+	fx := newGitHubFixture(t, true)
+	fx.debBytes["nameless_1_amd64.deb"] = testsupport.MinimalDeb("", "1", "amd64")
+	asset := ghAsset{BrowserDownloadURL: fx.srv.URL + "/acme/tools/releases/download/v1.2-3/nameless_1_amd64.deb", Digest: "sha256:00"}
+	_, err := newTestProvider().deriveAsset(context.Background(), fx.remote(), asset, "fp")
+	if !errors.Is(err, provider.ErrInvalidPackage) {
+		t.Fatalf("want ErrInvalidPackage, got %v", err)
+	}
+}