Request path not passed to proxy when $scheme is used in proxy_pass URI

[Ben Hoskings]

Hi all, I've found a strange behaviour with proxy_pass. I've reduced a
simple vhost that reproduces it:

server {
  listen 127.0.0.1:8000;
  location / {
    proxy_pass $scheme://127.0.0.1:9000/;
  }
}

A listener on localhost:9000 receives a request, but for '/' instead of the
correct path. For example, curling this URI...
> curl -I -X GET http://localhost:8000/test-path

... causes a "GET /" on a local listener:
> nc -l 127.0.0.1 9000
GET / HTTP/1.0

If I replace $scheme with 'http' (i.e. "proxy_pass http://127.0.0.1:9000/"),
then it works correctly:
> curl -I -X GET http://localhost:8000/test-path

> nc -l 127.0.0.1 9000
GET /test-path HTTP/1.0

I ran these tests on nginx-1.2.7 / OS X 10.8.3; the behaviour is the same
on nginx-1.2.4 / Ubuntu 12.04 (which is where I discovered it).

Am I using $scheme incorrectly here, or could this be a bug?

Cheers,
Ben Hoskings
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