changes to internal/archiver/archiver: allow restic backup to work with a repo size limitation

in saveDir() don't save the directory if the current backup is in repository shutdown mode

In saveTree() don't descend into subdirectories if the current backup is in repository shutdown mode

in Snapshot() add the flag PartialSnapshot to the Snapshot structure, also add tag "partial-snapshot"
to the tag list.

internal/archiver/archiver.go

@@ -15,6 +15,7 @@ import (
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/feature"
 	"github.com/restic/restic/internal/fs"
+	"github.com/restic/restic/internal/repository"
 	"github.com/restic/restic/internal/restic"
 	"golang.org/x/sync/errgroup"
 )
@@ -75,6 +76,7 @@ type archiverRepo interface {
 	restic.Loader
 	restic.BlobSaver
 	restic.SaverUnpacked[restic.WriteableFileType]
+	repository.CapacityChecker
 
 	Config() restic.Config
 	StartPackUploader(ctx context.Context, wg *errgroup.Group)
@@ -327,34 +329,37 @@ func (arch *Archiver) saveDir(ctx context.Context, snPath string, dir string, me
 		// test if context has been cancelled
 		if ctx.Err() != nil {
 			debug.Log("context has been cancelled, aborting")
+
 			return futureNode{}, ctx.Err()
 		}
 
 		pathname := arch.FS.Join(dir, name)
 		oldNode := previous.Find(name)
 		snItem := join(snPath, name)
-		fn, excluded, err := arch.save(ctx, snItem, pathname, oldNode)
+		// don't save if we are in repository shutdown mode
+		if !arch.Repo.MaxCapacityExceeded() {
+			fn, excluded, err := arch.save(ctx, snItem, pathname, oldNode)
 
-		// return error early if possible
-		if err != nil {
-			err = arch.error(pathname, err)
-			if err == nil {
-				// ignore error
+			// return error early if possible
+			if err != nil {
+				err = arch.error(pathname, err)
+				if err == nil {
+					// ignore error
+					continue
+				}
+
+				return futureNode{}, err
+			}
+
+			if excluded {
 				continue
 			}
 
-			return futureNode{}, err
+			nodes = append(nodes, fn)
 		}
-
-		if excluded {
-			continue
-		}
-
-		nodes = append(nodes, fn)
 	}
 
 	fn := arch.treeSaver.Save(ctx, snPath, dir, treeNode, nodes, complete)
-
 	return fn, nil
 }
 
@@ -717,14 +722,17 @@ func (arch *Archiver) saveTree(ctx context.Context, snPath string, atree *tree,
 			return futureNode{}, 0, err
 		}
 
-		// not a leaf node, archive subtree
-		fn, _, err := arch.saveTree(ctx, join(snPath, name), &subatree, oldSubtree, func(n *restic.Node, is ItemStats) {
-			arch.trackItem(snItem, oldNode, n, is, time.Since(start))
-		})
-		if err != nil {
-			return futureNode{}, 0, err
+		// don't descend into subdirectories if we are in shutdown mode
+		if !arch.Repo.MaxCapacityExceeded() {
+			// not a leaf node, archive subtree
+			fn, _, err := arch.saveTree(ctx, join(snPath, name), &subatree, oldSubtree, func(n *restic.Node, is ItemStats) {
+				arch.trackItem(snItem, oldNode, n, is, time.Since(start))
+			})
+			if err != nil {
+				return futureNode{}, 0, err
+			}
+			nodes = append(nodes, fn)
 		}
-		nodes = append(nodes, fn)
 	}
 
 	fn := arch.treeSaver.Save(ctx, snPath, atree.FileInfoPath, node, nodes, complete)
@@ -909,7 +917,6 @@ func (arch *Archiver) Snapshot(ctx context.Context, targets []string, opts Snaps
 			debug.Log("error while saving tree: %v", err)
 			return err
 		}
-
 		return arch.Repo.Flush(ctx)
 	})
 	err = wgUp.Wait()
@@ -924,6 +931,9 @@ func (arch *Archiver) Snapshot(ctx context.Context, targets []string, opts Snaps
 		}
 	}
 
+	if arch.Repo.MaxCapacityExceeded() {
+		opts.Tags = append(opts.Tags, "partial-snapshot")
+	}
 	sn, err := restic.NewSnapshot(targets, opts.Tags, opts.Hostname, opts.Time)
 	if err != nil {
 		return nil, restic.ID{}, nil, err
@@ -934,6 +944,10 @@ func (arch *Archiver) Snapshot(ctx context.Context, targets []string, opts Snaps
 	if opts.ParentSnapshot != nil {
 		sn.Parent = opts.ParentSnapshot.ID()
 	}
+	if arch.Repo.MaxCapacityExceeded() {
+		sn.PartialSnapshot = true
+	}
+
 	sn.Tree = &rootTreeID
 	arch.summary.BackupEnd = time.Now()
 	sn.Summary = &restic.SnapshotSummary{