resources: exec: Ignore signals sent to main process

When we send a ^C to the main process, our children see it too! This
puts them in their own process group so that they're not affected.
There's still the matter of properly hooking up the internal exit signal
to a proper shutdown, but that's separate.

This might mean that there should be a case for an interrupt aspect to
the resource API which would allow a second ^C by the engine, to cause a
forceful termination by the resource if that resource supported that.

resources/exec.go

@@ -114,6 +114,11 @@ func (obj *ExecRes) Watch() error {
 		}
 		cmd := exec.Command(cmdName, cmdArgs...)
 		//cmd.Dir = "" // look for program in pwd ?
+		// ignore signals sent to parent process (we're in our own group)
+		cmd.SysProcAttr = &syscall.SysProcAttr{
+			Setpgid: true,
+			Pgid:    0,
+		}
 
 		cmdReader, err := cmd.StdoutPipe()
 		if err != nil {
@@ -197,6 +202,11 @@ func (obj *ExecRes) CheckApply(apply bool) (bool, error) {
 			cmdArgs = []string{"-c", obj.IfCmd}
 		}
 		cmd := exec.Command(cmdName, cmdArgs...)
+		// ignore signals sent to parent process (we're in our own group)
+		cmd.SysProcAttr = &syscall.SysProcAttr{
+			Setpgid: true,
+			Pgid:    0,
+		}
 		if err := cmd.Run(); err != nil {
 			// TODO: check exit value
 			return true, nil // don't run
@@ -228,6 +238,12 @@ func (obj *ExecRes) CheckApply(apply bool) (bool, error) {
 	}
 	cmd := exec.Command(cmdName, cmdArgs...)
 	//cmd.Dir = "" // look for program in pwd ?
+	// ignore signals sent to parent process (we're in our own group)
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Setpgid: true,
+		Pgid:    0,
+	}
+
 	var out bytes.Buffer
 	cmd.Stdout = &out