container/stub: export stub helpers

These are very useful in many packages containing relatively large amount of code making calls to difficult or impossible to stub functions.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/stub/exit.go

@@ -0,0 +1,15 @@
+package stub
+
+// PanicExit is a magic panic value treated as a simulated exit.
+const PanicExit = 0xdeadbeef
+
+// HandleExit must be deferred before calling with the stub.
+func HandleExit() {
+	r := recover()
+	if r == PanicExit {
+		return
+	}
+	if r != nil {
+		panic(r)
+	}
+}