rock5b: ignore lost+found when preserving partition

As this fork uses ext4 for the `BOOT` partition for compatibility
with the vendor U-Boot, `/lost+found` exists on that (unlike the
xfs partitions, which do not).

As a result, the archiver needs to be ignored when preserving the
filesystem or the installer will fail at upgrade to to the directory
already existing on the new partition.

For safety/sanity, any files in `/lost+found` are also ignored.
Given that `/boot` is read-only, there isn't really anything we
should ever need to manually restore from this partition.

This is intended to fix upgrades without `--preserve`.

cmd/installer/pkg/install/manifest.go

@@ -506,9 +506,10 @@ func (m *Manifest) preserveContents(device Device, targets []*Target) (err error
 		}
 
 		var (
-			sourcePart     *gpt.Partition
-			fileSystemType partition.FileSystemType
-			fnmatchFilters []string
+			sourcePart      *gpt.Partition
+			fileSystemType  partition.FileSystemType
+			fnmatchFilters  []string
+			fnignoreFilters []string
 		)
 
 		sources := append(
@@ -528,6 +529,17 @@ func (m *Manifest) preserveContents(device Device, targets []*Target) (err error
 					fileSystemType = source.FileSystemType
 					fnmatchFilters = source.FnmatchFilters
 
+					// HACK: for ext filesystems, the lost+found directory will
+					// already exist. we'll go ahead and ignore it AND its
+					// contents if it has any (/boot isn't r-w, so there isn't
+					// anything we'd ever need to recover from it)
+					if source.FileSystemType == partition.FilesystemTypeExt4 {
+						fnignoreFilters = []string{
+							"lost+found",
+							"lost+found/*",
+						}
+					}
+
 					break
 				}
 			}
@@ -543,7 +555,7 @@ func (m *Manifest) preserveContents(device Device, targets []*Target) (err error
 			continue
 		}
 
-		if err = target.SaveContents(device, sourcePart, fileSystemType, fnmatchFilters); err != nil {
+		if err = target.SaveContents(device, sourcePart, fileSystemType, fnmatchFilters, fnignoreFilters); err != nil {
 			log.Printf("warning: failed to preserve contents of %q on %q: %s", target.Label, device.Device, err)
 		}
 	}

cmd/installer/pkg/install/target.go

@@ -332,6 +332,7 @@ func (t *Target) SaveContents(
 	source *gpt.Partition,
 	fileSystemType partition.FileSystemType,
 	fnmatchFilters []string,
+	fnignoreFilters []string,
 ) error {
 	partPath, err := util.PartPath(device.Device, int(source.Number))
 	if err != nil {
@@ -341,7 +342,7 @@ func (t *Target) SaveContents(
 	if fileSystemType == partition.FilesystemTypeNone {
 		err = t.saveRawContents(partPath)
 	} else {
-		err = t.saveFilesystemContents(partPath, fileSystemType, fnmatchFilters)
+		err = t.saveFilesystemContents(partPath, fileSystemType, fnmatchFilters, fnignoreFilters)
 	}
 
 	if err != nil {
@@ -380,6 +381,7 @@ func (t *Target) saveFilesystemContents(
 	partPath string,
 	fileSystemType partition.FileSystemType,
 	fnmatchFilters []string,
+	fnignoreFilters []string,
 ) error {
 	t.Contents = bytes.NewBuffer(nil)
 
@@ -390,6 +392,7 @@ func (t *Target) saveFilesystemContents(
 				mountPath,
 				t.Contents,
 				archiver.WithFnmatchPatterns(fnmatchFilters...),
+				archiver.WithFnignorePatterns(fnignoreFilters...),
 			)
 		},
 	)

pkg/archiver/walker.go

@@ -31,10 +31,11 @@ const (
 )
 
 type walkerOptions struct {
-	skipRoot        bool
-	maxRecurseDepth int
-	fnmatchPatterns []string
-	types           map[FileType]struct{}
+	skipRoot         bool
+	maxRecurseDepth  int
+	fnmatchPatterns  []string
+	fnignorePatterns []string
+	types            map[FileType]struct{}
 }
 
 // WalkerOption configures Walker.
@@ -65,6 +66,15 @@ func WithFnmatchPatterns(patterns ...string) WalkerOption {
 	}
 }
 
+// WithFnignorePatterns ignores results matching any of the patterns.
+//
+// Default is not to do any ignoring.
+func WithFnignorePatterns(patterns ...string) WalkerOption {
+	return func(o *walkerOptions) {
+		o.fnignorePatterns = append(o.fnignorePatterns, patterns...)
+	}
+}
+
 // WithFileTypes filters results by file types.
 //
 // Default is not to do any filtering.
@@ -166,6 +176,14 @@ func Walker(ctx context.Context, rootPath string, options ...WalkerOption) (<-ch
 				}
 			}
 
+			if item.Error == nil && len(opts.fnignorePatterns) > 0 {
+				for _, pattern := range opts.fnignorePatterns {
+					if matches, _ := filepath.Match(pattern, item.RelPath); matches { //nolint:errcheck
+						return nil
+					}
+				}
+			}
+
 			select {
 			case <-ctx.Done():
 				return ctx.Err()