lnd+chanbackup: add lnd config flag

In this commit, we add the --no-backup-archive with a default
as false. When set to true then previous channel backup file will
not be archived but replaced. We also modify TestUpdateAndSwap
test to make sure the new behaviour works as expected.

chanbackup/backupfile_test.go

@@ -48,7 +48,9 @@ func assertFileDeleted(t *testing.T, filePath string) {
 // TestUpdateAndSwap test that we're able to properly swap out old backups on
 // disk with new ones. Additionally, after a swap operation succeeds, then each
 // time we should only have the main backup file on disk, as the temporary file
-// has been removed.
+// has been removed. Finally, we check for noBackupArchive to ensure that the
+// archive file is created when it's set to false, and not created when it's
+// set to true.
 func TestUpdateAndSwap(t *testing.T) {
 	t.Parallel()
 
@@ -58,7 +60,8 @@ func TestUpdateAndSwap(t *testing.T) {
 		fileName     string
 		tempFileName string
 
-		oldTempExists bool
+		oldTempExists   bool
+		noBackupArchive bool
 
 		valid bool
 	}{
@@ -92,9 +95,37 @@ func TestUpdateAndSwap(t *testing.T) {
 			),
 			valid: true,
 		},
+
+		// Test with noBackupArchive set to true - should not create
+		// archive.
+		{
+			fileName: filepath.Join(
+				tempTestDir, DefaultBackupFileName,
+			),
+			tempFileName: filepath.Join(
+				tempTestDir, DefaultTempBackupFileName,
+			),
+			noBackupArchive: true,
+			valid:           true,
+		},
+
+		// Test with v set to false - should create
+		// archive.
+		{
+			fileName: filepath.Join(
+				tempTestDir, DefaultBackupFileName,
+			),
+			tempFileName: filepath.Join(
+				tempTestDir, DefaultTempBackupFileName,
+			),
+			noBackupArchive: false,
+			valid:           true,
+		},
 	}
 	for i, testCase := range testCases {
-		backupFile := NewMultiFile(testCase.fileName)
+		backupFile := NewMultiFile(
+			testCase.fileName, testCase.noBackupArchive,
+		)
 
 		// To start with, we'll make a random byte slice that'll pose
 		// as our packed multi backup.
@@ -160,6 +191,41 @@ func TestUpdateAndSwap(t *testing.T) {
 		// Additionally, we shouldn't be able to find the temp backup
 		// file on disk, as it should be deleted each time.
 		assertFileDeleted(t, testCase.tempFileName)
+
+		// Now check if archive was created when noBackupArchive is
+		// false.
+		archiveDir := filepath.Join(
+			filepath.Dir(testCase.fileName),
+			DefaultChanBackupArchiveDirName,
+		)
+		if !testCase.noBackupArchive {
+			files, err := os.ReadDir(archiveDir)
+			require.NoError(t, err)
+			require.Len(t, files, 1)
+
+			// Verify the archive contents match the previous
+			// backup.
+			archiveFile := filepath.Join(
+				archiveDir, files[0].Name(),
+			)
+			// The archived content should match the previous
+			// backup (newPackedMulti) that was just swapped out.
+			assertBackupMatches(t, archiveFile, newPackedMulti)
+
+			// Clean up the archive directory.
+			os.RemoveAll(archiveDir)
+
+			continue
+		}
+
+		// When noBackupArchive is true, no new archive file should be
+		// created. Note: In a real environment, the archive directory
+		// might exist with older backups before the feature is
+		// disabled, but for test simplicity (since we clean up the
+		// directory between test cases), we verify the directory
+		// doesn't exist at all.
+		require.NoDirExists(t, archiveDir)
+
 	}
 }
 
@@ -238,7 +304,7 @@ func TestExtractMulti(t *testing.T) {
 	}
 	for i, testCase := range testCases {
 		// First, we'll make our backup file with the specified name.
-		backupFile := NewMultiFile(testCase.fileName)
+		backupFile := NewMultiFile(testCase.fileName, false)
 
 		// With our file made, we'll now attempt to read out the
 		// multi-file.
@@ -292,12 +358,18 @@ func TestCreateArchiveFile(t *testing.T) {
 	require.NoError(t, err)
 
 	tests := []struct {
-		name      string
-		setup     func()
-		wantError bool
+		name            string
+		setup           func()
+		noBackupArchive bool
+		wantError       bool
 	}{
 		{
-			name: "successful archive",
+			name:            "successful archive",
+			noBackupArchive: false,
+		},
+		{
+			name:            "skip archive when disabled",
+			noBackupArchive: true,
 		},
 		{
 			name: "invalid archive directory permissions",
@@ -306,7 +378,8 @@ func TestCreateArchiveFile(t *testing.T) {
 				err := os.MkdirAll(archiveDir, 0500)
 				require.NoError(t, err)
 			},
-			wantError: true,
+			noBackupArchive: false,
+			wantError:       true,
 		},
 	}
 
@@ -318,7 +391,9 @@ func TestCreateArchiveFile(t *testing.T) {
 				tc.setup()
 			}
 
-			multiFile := NewMultiFile(backupFile)
+			multiFile := NewMultiFile(
+				backupFile, tc.noBackupArchive,
+			)
 
 			err := multiFile.createArchiveFile()
 			if tc.wantError {
@@ -328,6 +403,13 @@ func TestCreateArchiveFile(t *testing.T) {
 
 			require.NoError(t, err)
 
+			// If archiving is disabled, verify no archive was
+			// created.
+			if tc.noBackupArchive {
+				require.NoDirExists(t, archiveDir)
+				return
+			}
+
 			// Verify archive exists and content matches.
 			files, err := os.ReadDir(archiveDir)
 			require.NoError(t, err)