location is case insensitive but rewrite-target isn't

[bsuh]

Is this a request for help? (If yes, you should use our troubleshooting guide and community support channels, see https://kubernetes.io/docs/tasks/debug-application-cluster/troubleshooting/.):

What keywords did you search in NGINX Ingress controller issues before filing this one? (If you have found any duplicates, you should instead reply there.):

"rewrite" "case" "sensitivity"

---

Is this a BUG REPORT or FEATURE REQUEST? (choose one): BUG REPORT

NGINX Ingress controller version: 0.16.2

Kubernetes version (use kubectl version): 1.10.5

Environment:

• Cloud provider or hardware configuration: Don't know
• OS (e.g. from /etc/os-release): Canonical Distribution of Kubernetes
• Kernel (e.g. uname -a): Don't have access
• Install tools:
• Others:

What happened: Go to a path with rewrite-target annotation '/' using a different case. Path doesn't get trimmed.

What you expected to happen: Path gets trimmed.

How to reproduce it (as minimally and precisely as possible):

apiVersion: v1
kind: Service
metadata:
  name: postman-echo
spec:
  type: ExternalName
  externalName: postman-echo.com
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: rewrite-case-ingress
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
      http:
        paths:
          - backend:
              serviceName: postman-echo
              servicePort: 80
            path: /postman-echo

curl http://.../postman-echo/get works
curl http://.../Postman-echo/get returns 404

Generated nginx.conf:

                location ~* ^/postman-echo\/?(?<baseuri>.*) {
...

                        rewrite /postman-echo/(.*) /$1 break;
                        rewrite /postman-echo / break;
...

Anything else we need to know: