Enable iterative manifests with 0 file count

When a bundle is updated to only modify which bundles are included, an
iterative manifest can be generated with 0 files. This change adds a
type field to the Manifest struct to determine when an iterative
manifest is used and allows the creation of iterative manifests with
a 0 file count.

Fixes #516

Signed-off-by: John Akre <john.w.akre@intel.com>

swupd/create_manifests.go

@@ -82,6 +82,7 @@ func initBundles(ui UpdateInfo, c config, numWorkers int) ([]*Manifest, error) {
 					TimeStamp: ui.timeStamp,
 				},
 				Name: bundleName,
+				Type: ManifestBundle,
 			}
 
 			if bundleName == "full" {
@@ -459,6 +460,7 @@ func CreateManifests(version uint32, minVersion uint32, format uint, statedir st
 			Previous:   lastVersion,
 			TimeStamp:  timeStamp,
 		},
+		Type: ManifestMoM,
 	}
 	// if min-version wasn't explicitly set we need to carry the header forward
 	// from the old MoM

swupd/manifest.go

@@ -40,6 +40,19 @@ const IndexBundle = "os-core-update-index"
 // this should be done when configuration is in a more stable state
 const indexAllBundleDir = "/usr/share/clear/allbundles"
 
+// ManifestType specifies whether the manifest is a MoM, bundle, iterative, or
+// delta manifest.
+type ManifestType uint8
+
+// Valid values for ManifestType.
+const (
+	ManifestUnset ManifestType = iota
+	ManifestMoM
+	ManifestBundle
+	ManifestIterative
+	ManifestDelta
+)
+
 // ManifestHeader contains metadata for the manifest
 type ManifestHeader struct {
 	Format      uint
@@ -59,6 +72,7 @@ type Manifest struct {
 	Files        []*File
 	DeletedFiles []*File
 	BundleInfo   BundleInfo
+	Type         ManifestType
 }
 
 // MoM is a manifest that holds references to bundle manifests.
@@ -183,7 +197,9 @@ func (m *Manifest) CheckHeaderIsValid() error {
 	if m.Header.Version == 0 {
 		return errors.New("manifest has version zero, version must be positive")
 	}
-	if m.Header.FileCount == 0 {
+
+	// Iterative manifests updated to include new bundles can have 0 files.
+	if m.Header.FileCount == 0 && m.Type != ManifestIterative {
 		return errors.New("manifest has a zero file count")
 	}
 
@@ -310,6 +326,7 @@ func (m *Manifest) createIterativeManifest(fromVersion uint32) *Manifest {
 		Header:     m.Header,
 		Name:       fmt.Sprintf("%s.I.%d", m.Name, m.Header.Previous),
 		BundleInfo: m.BundleInfo,
+		Type:       ManifestIterative,
 	}
 	fm.Header.ContentSize = 0
 

swupd/packs.go

@@ -237,6 +237,7 @@ func WritePack(w io.Writer, fromManifest, toManifest *Manifest, outputDir, chroo
 		dManifest = &Manifest{
 			Header: fromManifest.Header,
 			Name:   fromManifest.Name,
+			Type:   ManifestDelta,
 		}
 		dManifest.Header.ContentSize = 0