feat(snapshots): Implement volume shadow copy support on Windows (#3543)

* Implement volume shadow copy support on Windows

* Update go-vss version

* Fix unused variables

* Rename upload_actions*.go files

* Move vss settings to a separate policy section

* Handle existing shadow copy root

* Fix tests

* Fix lint issues

* Add cli policy test

* Add OS snapshot integration test

* Add GitHub Actions VSS test

* Fix "Incorrect function" error for root VSS snapshots

* Rename err to finalErr in createOSSnapshot

* Add OSSnapshotMode test

* Do not modify paths starting with \\?\ on Windows

* Allow warning messages in logfile tests

* Fix ignorefs not wrapping OS snapshot directory

* Retry VSS creation if another op was in progress

---------

Co-authored-by: Jarek Kowalski <jaak@jkowalski.net>

cli/command_policy_set.go

@@ -24,6 +24,7 @@ type commandPolicySet struct {
 	policyLoggingFlags
 	policyRetentionFlags
 	policySchedulingFlags
+	policyOSSnapshotFlags
 	policyUploadFlags
 }
 
@@ -39,6 +40,7 @@ func (c *commandPolicySet) setup(svc appServices, parent commandParent) {
 	c.policyLoggingFlags.setup(cmd)
 	c.policyRetentionFlags.setup(cmd)
 	c.policySchedulingFlags.setup(cmd)
+	c.policyOSSnapshotFlags.setup(cmd)
 	c.policyUploadFlags.setup(cmd)
 
 	cmd.Action(svc.repositoryWriterAction(c.run))
@@ -112,6 +114,10 @@ func (c *commandPolicySet) setPolicyFromFlags(ctx context.Context, p *policy.Pol
 		return errors.Wrap(err, "actions policy")
 	}
 
+	if err := c.setOSSnapshotPolicyFromFlags(ctx, &p.OSSnapshotPolicy, changeCount); err != nil {
+		return errors.Wrap(err, "OS snapshot policy")
+	}
+
 	if err := c.setLoggingPolicyFromFlags(ctx, &p.LoggingPolicy, changeCount); err != nil {
 		return errors.Wrap(err, "actions policy")
 	}

cli/command_policy_set_os_snapshot.go

@@ -0,0 +1,64 @@
+package cli
+
+import (
+	"context"
+
+	"github.com/alecthomas/kingpin/v2"
+	"github.com/pkg/errors"
+
+	"github.com/kopia/kopia/snapshot/policy"
+)
+
+type policyOSSnapshotFlags struct {
+	policyEnableVolumeShadowCopy string
+}
+
+func (c *policyOSSnapshotFlags) setup(cmd *kingpin.CmdClause) {
+	osSnapshotMode := []string{policy.OSSnapshotNeverString, policy.OSSnapshotAlwaysString, policy.OSSnapshotWhenAvailableString, inheritPolicyString}
+
+	cmd.Flag("enable-volume-shadow-copy", "Enable Volume Shadow Copy snapshots ('never', 'always', 'when-available', 'inherit')").PlaceHolder("MODE").EnumVar(&c.policyEnableVolumeShadowCopy, osSnapshotMode...)
+}
+
+func (c *policyOSSnapshotFlags) setOSSnapshotPolicyFromFlags(ctx context.Context, fp *policy.OSSnapshotPolicy, changeCount *int) error {
+	if err := applyPolicyOSSnapshotMode(ctx, "enable volume shadow copy", &fp.VolumeShadowCopy.Enable, c.policyEnableVolumeShadowCopy, changeCount); err != nil {
+		return errors.Wrap(err, "enable volume shadow copy")
+	}
+
+	return nil
+}
+
+func applyPolicyOSSnapshotMode(ctx context.Context, desc string, val **policy.OSSnapshotMode, str string, changeCount *int) error {
+	if str == "" {
+		// not changed
+		return nil
+	}
+
+	var mode policy.OSSnapshotMode
+
+	switch str {
+	case inheritPolicyString, defaultPolicyString:
+		*changeCount++
+
+		log(ctx).Infof(" - resetting %q to a default value inherited from parent.", desc)
+
+		*val = nil
+
+		return nil
+	case policy.OSSnapshotNeverString:
+		mode = policy.OSSnapshotNever
+	case policy.OSSnapshotAlwaysString:
+		mode = policy.OSSnapshotAlways
+	case policy.OSSnapshotWhenAvailableString:
+		mode = policy.OSSnapshotWhenAvailable
+	default:
+		return errors.Errorf("invalid %q mode %q", desc, str)
+	}
+
+	*changeCount++
+
+	log(ctx).Infof(" - setting %q to %v.", desc, mode)
+
+	*val = &mode
+
+	return nil
+}

cli/command_policy_set_os_snapshot_test.go

@@ -0,0 +1,42 @@
+package cli_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/kopia/kopia/internal/testutil"
+	"github.com/kopia/kopia/tests/testenv"
+)
+
+func TestSetOSSnapshotPolicy(t *testing.T) {
+	e := testenv.NewCLITest(t, testenv.RepoFormatNotImportant, testenv.NewInProcRunner(t))
+	defer e.RunAndExpectSuccess(t, "repo", "disconnect")
+
+	e.RunAndExpectSuccess(t, "repo", "create", "filesystem", "--path", e.RepoDir)
+
+	lines := e.RunAndExpectSuccess(t, "policy", "show", "--global")
+	lines = compressSpaces(lines)
+	require.Contains(t, lines, " Volume Shadow Copy: when-available (defined for this target)")
+
+	// make some directory we'll be setting policy on
+	td := testutil.TempDirectory(t)
+
+	lines = e.RunAndExpectSuccess(t, "policy", "show", td)
+	lines = compressSpaces(lines)
+	require.Contains(t, lines, " Volume Shadow Copy: when-available inherited from (global)")
+
+	e.RunAndExpectSuccess(t, "policy", "set", "--global", "--enable-volume-shadow-copy=always")
+
+	lines = e.RunAndExpectSuccess(t, "policy", "show", td)
+	lines = compressSpaces(lines)
+
+	require.Contains(t, lines, " Volume Shadow Copy: always inherited from (global)")
+
+	e.RunAndExpectSuccess(t, "policy", "set", "--enable-volume-shadow-copy=never", td)
+
+	lines = e.RunAndExpectSuccess(t, "policy", "show", td)
+	lines = compressSpaces(lines)
+
+	require.Contains(t, lines, " Volume Shadow Copy: never (defined for this target)")
+}

cli/command_policy_show.go

@@ -128,6 +128,8 @@ func printPolicy(out *textOutput, p *policy.Policy, def *policy.Definition) {
 	rows = append(rows, policyTableRow{})
 	rows = appendActionsPolicyRows(rows, p, def)
 	rows = append(rows, policyTableRow{})
+	rows = appendOSSnapshotPolicyRows(rows, p, def)
+	rows = append(rows, policyTableRow{})
 	rows = appendLoggingPolicyRows(rows, p, def)
 
 	out.printStdout("Policy for %v:\n\n%v\n", p.Target(), alignedPolicyTableRows(rows))
@@ -449,6 +451,15 @@ func appendActionCommandRows(rows []policyTableRow, h *policy.ActionCommand) []p
 	return rows
 }
 
+func appendOSSnapshotPolicyRows(rows []policyTableRow, p *policy.Policy, def *policy.Definition) []policyTableRow {
+	rows = append(rows,
+		policyTableRow{"OS-level snapshot support:", "", ""},
+		policyTableRow{"  Volume Shadow Copy:", p.OSSnapshotPolicy.VolumeShadowCopy.Enable.String(), definitionPointToString(p.Target(), def.OSSnapshotPolicy.VolumeShadowCopy.Enable)},
+	)
+
+	return rows
+}
+
 func valueOrNotSet(p *policy.OptionalInt) string {
 	if p == nil {
 		return "-"