Add APFS snapshot support

Add's VSS support for macOS using APFS snapshot's

src/duplicacy_shadowcopy.go

@@ -3,6 +3,7 @@
 // Commercial use requires per-user licenses available from https://duplicacy.com
 
 // +build !windows
+// +build !darwin
 
 package duplicacy
 

src/duplicacy_shadowcopy_osx.go

@@ -0,0 +1,106 @@
+//
+// Shadow copy module for Mac OSX using APFS snapshot
+//
+//
+// This module copyright 2018 Adam Marcus (https://github.com/amarcu5)
+// and may be distributed under the same terms as Duplicacy.
+
+package duplicacy
+
+import (
+	"os"
+	"strings"
+	"io/ioutil"
+	"os/exec"
+	"context"
+	"errors"
+	"time"
+)
+
+var snapshotPath string
+var snapshotDate string
+
+func CommandWithTimeout(timeoutInSeconds int, name string, arg ...string) (output string, err error) {
+  
+  ctx, cancel := context.WithTimeout(context.Background(), time.Duration(timeoutInSeconds) * time.Second)
+	defer cancel() 
+	
+	cmd := exec.CommandContext(ctx, name, arg...)
+	out, err := cmd.Output()
+	
+  if ctx.Err() == context.DeadlineExceeded {
+    err = errors.New("Command '" + name + "' timed out")
+	}
+	
+	output = string(out)
+	return output, err;
+}
+
+func DeleteShadowCopy() {
+  
+  if snapshotPath == "" {
+    return
+  }
+
+	err := exec.Command("umount", "-f", snapshotPath).Run()
+  if err != nil {
+    LOG_ERROR("VSS_DELETE", "Error while unmounting snapshot")
+		return
+	}
+	
+	err = exec.Command("tmutil", "deletelocalsnapshots", snapshotDate).Run()
+  if err != nil {
+    LOG_ERROR("VSS_DELETE", "Error while deleting local snapshot")
+		return
+	}
+  
+  os.RemoveAll(snapshotPath)
+  
+  LOG_INFO("VSS_DELETE", "Shadow copy unmounted and deleted at %s", snapshotPath)
+    
+  snapshotPath = ""
+  
+}
+
+func CreateShadowCopy(top string, shadowCopy bool, timeoutInSeconds int) (shadowTop string) {
+
+	if !shadowCopy {
+		return top
+	}
+
+	if timeoutInSeconds <= 60 {
+		timeoutInSeconds = 60
+	}
+	
+  tmpDir, err := ioutil.TempDir("/tmp/", "snp_")
+	if err != nil {
+    LOG_ERROR("VSS_CREATE", "Failed to create temporary mount directory")
+		return top
+	}
+	snapshotPath = tmpDir
+	
+	tmutilOutput, err := CommandWithTimeout(timeoutInSeconds, "tmutil", "snapshot", "/")
+  if err != nil {
+    LOG_ERROR("VSS_CREATE", "Error while calling tmutil: " + err.Error())
+		return top
+	}
+    
+	colonPos := strings.IndexByte(tmutilOutput, ':')
+	if colonPos < 0 {
+    LOG_ERROR("VSS_CREATE", "Snapshot creation failed")
+		return top
+	}
+	snapshotDate = strings.TrimSpace(tmutilOutput[colonPos+1:])
+	
+	_, err = CommandWithTimeout(timeoutInSeconds, "mount", "-t", "apfs", "-o", "nobrowse,-s=com.apple.TimeMachine." + snapshotDate, "/", snapshotPath)
+  if err != nil {
+    LOG_ERROR("VSS_CREATE", "Error while mounting snapshot: " + err.Error())
+		return top
+	}
+
+  LOG_DEBUG("VSS_PROPERTY", "Returned path: %s", snapshotPath + top)
+
+  LOG_INFO("VSS_DONE", "Shadow copy created and mounted at %s", snapshotPath)
+	
+	return snapshotPath + top
+}