Initial QSfera import

Server/vendor/github.com/moby/go-archive/diff_unix.go

@@ -0,0 +1,21 @@
+//go:build !windows
+
+package archive
+
+import "golang.org/x/sys/unix"
+
+// overrideUmask sets current process's file mode creation mask to newmask
+// and returns a function to restore it.
+//
+// WARNING for readers stumbling upon this code. Changing umask in a multi-
+// threaded environment isn't safe. Don't use this without understanding the
+// risks, and don't export this function for others to use (we shouldn't even
+// be using this ourself).
+//
+// FIXME(thaJeztah): we should get rid of these hacks if possible.
+func overrideUmask(newMask int) func() {
+	oldMask := unix.Umask(newMask)
+	return func() {
+		unix.Umask(oldMask)
+	}
+}