mount: set DirectMount: true

Attempt to directly call mount(2) before trying fusermount. This means we
can do without fusermount if running as root.

https://github.com/rfjakob/gocryptfs/issues/697

README.md

@@ -195,6 +195,11 @@ RM:    2,367
 Changelog
 ---------
 
+#### vNEXT, in progress
+* Attempt to directly call mount(2) before trying fusermount. This means we
+  can do without fusermount if running as root or in a root-like namespace
+  ([#697](https://github.com/rfjakob/gocryptfs/issues/697)).
+
 #### v2.3.2, 2023-04-29
 * Fix incorrect file size reported after hard link creation
   ([#724](https://github.com/rfjakob/gocryptfs/issues/724))

mount.go

@@ -396,6 +396,9 @@ func initGoFuse(rootNode fs.InodeEmbedder, args *argContainer) *fuse.Server {
 		// Setting SyncRead disables FUSE_CAP_ASYNC_READ. This makes the kernel
 		// do everything in-order without parallelism.
 		SyncRead: args.serialize_reads,
+		// Attempt to directly call mount(2) before trying fusermount. This means we
+		// can do without fusermount if running as root.
+		DirectMount: true,
 	}
 
 	mOpts := &fuseOpts.MountOptions