restore: use case insensitive file name comparison on windows

internal/restorer/restorer.go

@@ -480,11 +480,11 @@ func (res *Restorer) removeUnexpectedFiles(target, location string, expectedFile
 
 	keep := map[string]struct{}{}
 	for _, name := range expectedFilenames {
-		keep[name] = struct{}{}
+		keep[toComparableFilename(name)] = struct{}{}
 	}
 
 	for _, entry := range entries {
-		if _, ok := keep[entry]; ok {
+		if _, ok := keep[toComparableFilename(entry)]; ok {
 			continue
 		}
 

internal/restorer/restorer_unix.go

@@ -0,0 +1,10 @@
+//go:build !windows
+// +build !windows
+
+package restorer
+
+// toComparableFilename returns a filename suitable for equality checks. On Windows, it returns the
+// uppercase version of the string. On all other systems, it returns the unmodified filename.
+func toComparableFilename(path string) string {
+	return path
+}

internal/restorer/restorer_windows.go

@@ -0,0 +1,13 @@
+//go:build windows
+// +build windows
+
+package restorer
+
+import "strings"
+
+// toComparableFilename returns a filename suitable for equality checks. On Windows, it returns the
+// uppercase version of the string. On all other systems, it returns the unmodified filename.
+func toComparableFilename(path string) string {
+	// apparently NTFS internally uppercases filenames for comparision
+	return strings.ToUpper(path)
+}

internal/restorer/restorer_windows_test.go

@@ -9,6 +9,7 @@ import (
 	"math"
 	"os"
 	"path"
+	"path/filepath"
 	"syscall"
 	"testing"
 	"time"
@@ -539,3 +540,36 @@ func TestDirAttributeCombinationsOverwrite(t *testing.T) {
 		}
 	}
 }
+
+func TestRestoreDeleteCaseInsensitive(t *testing.T) {
+	repo := repository.TestRepository(t)
+	tempdir := rtest.TempDir(t)
+
+	sn, _ := saveSnapshot(t, repo, Snapshot{
+		Nodes: map[string]Node{
+			"anotherfile": File{Data: "content: file\n"},
+		},
+	}, noopGetGenericAttributes)
+
+	// should delete files that no longer exist in the snapshot
+	deleteSn, _ := saveSnapshot(t, repo, Snapshot{
+		Nodes: map[string]Node{
+			"AnotherfilE": File{Data: "content: file\n"},
+		},
+	}, noopGetGenericAttributes)
+
+	res := NewRestorer(repo, sn, Options{})
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	err := res.RestoreTo(ctx, tempdir)
+	rtest.OK(t, err)
+
+	res = NewRestorer(repo, deleteSn, Options{Delete: true})
+	err = res.RestoreTo(ctx, tempdir)
+	rtest.OK(t, err)
+
+	// anotherfile must still exist
+	_, err = os.Stat(filepath.Join(tempdir, "anotherfile"))
+	rtest.OK(t, err)
+}