backup: rework error reporting for subcommand

cmd/restic/cmd_backup.go

@@ -633,8 +633,6 @@ func runBackup(ctx context.Context, opts BackupOptions, gopts GlobalOptions, ter
 		wg.Go(func() error { return sc.Scan(cancelCtx, targets) })
 	}
 
-	snapshotCtx, cancelSnapshot := context.WithCancel(ctx)
-
 	arch := archiver.New(repo, targetFS, archiver.Options{ReadConcurrency: backupOptions.ReadConcurrency})
 	arch.SelectByName = selectByNameFilter
 	arch.Select = selectFilter
@@ -642,12 +640,13 @@ func runBackup(ctx context.Context, opts BackupOptions, gopts GlobalOptions, ter
 	success := true
 	arch.Error = func(item string, err error) error {
 		success = false
+		reterr := progressReporter.Error(item, err)
 		// If we receive a fatal error during the execution of the snapshot,
 		// we abort the snapshot.
-		if errors.IsFatal(err) {
-			cancelSnapshot()
+		if reterr == nil && errors.IsFatal(err) {
+			reterr = err
 		}
-		return progressReporter.Error(item, err)
+		return reterr
 	}
 	arch.CompleteItem = progressReporter.CompleteItem
 	arch.StartFile = progressReporter.StartFile
@@ -674,8 +673,7 @@ func runBackup(ctx context.Context, opts BackupOptions, gopts GlobalOptions, ter
 	if !gopts.JSON {
 		progressPrinter.V("start backup on %v", targets)
 	}
-	_, id, err := arch.Snapshot(snapshotCtx, targets, snapshotOpts)
-	cancelSnapshot()
+	_, id, err := arch.Snapshot(ctx, targets, snapshotOpts)
 
 	// cleanly shutdown all running goroutines
 	cancel()

internal/archiver/file_saver.go

@@ -2,6 +2,7 @@ package archiver
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"os"
 	"sync"
@@ -146,7 +147,7 @@ func (s *FileSaver) saveFile(ctx context.Context, chnker *chunker.Chunker, snPat
 				panic("completed twice")
 			}
 			isCompleted = true
-			fnr.err = err
+			fnr.err = fmt.Errorf("failed to save %v: %w", target, err)
 			fnr.node = nil
 			fnr.stats = ItemStats{}
 			finish(fnr)

internal/fs/fs_reader_command.go

@@ -83,7 +83,7 @@ func (fp *CommandReader) wait() error {
 	err := fp.cmd.Wait()
 	if err != nil {
 		// Use a fatal error to abort the snapshot.
-		return errors.Fatal(err.Error())
+		return errors.Fatal(fmt.Errorf("command failed: %w", err).Error())
 	}
 	return nil
 }