disable index uploads for prune command

+ modifications of changelog

changelog/unreleased/pull-2773

@@ -1,8 +1,6 @@
-Enhancement: Optimize repository implementation
+Enhancement: Optimize handling of new index entries
-
-We've optimized the implementation of handling index entries in the repository.
 
 Restic now uses less memory for backups which add a lot of data, e.g. large initial backups.
-Also it is more stable in some edge situations and allows easier future enhancments.
+In addition, we've improved the stability in some edge cases.
 
 https://github.com/restic/restic/pull/2773

cmd/restic/cmd_prune.go

@@ -87,6 +87,9 @@ func runPrune(gopts GlobalOptions) error {
 		return err
 	}
 
+	// we do not need index updates while pruning!
+	repo.DisableAutoIndexUpdate()
+
 	return pruneRepository(gopts, repo)
 }
 

internal/repository/packer_manager.go

@@ -140,6 +140,9 @@ func (r *Repository) savePacker(ctx context.Context, t restic.BlobType, p *Packe
 	r.idx.StorePack(id, p.Packer.Blobs())
 
 	// Save index if full
+	if r.noAutoIndexUpdate {
+		return nil
+	}
 	return r.SaveFullIndex(ctx)
 }
 

internal/repository/repository.go

@@ -28,6 +28,7 @@ type Repository struct {
 	keyName string
 	idx     *MasterIndex
 	restic.Cache
+	noAutoIndexUpdate bool
 
 	treePM *packerManager
 	dataPM *packerManager
@@ -45,6 +46,10 @@ func New(be restic.Backend) *Repository {
 	return repo
 }
 
+func (r *Repository) DisableAutoIndexUpdate() {
+	r.noAutoIndexUpdate = true
+}
+
 // Config returns the repository configuration.
 func (r *Repository) Config() restic.Config {
 	return r.cfg