Fix crash on remote connection when GIT_PROXY_AUTO is set but no proxy is detected

[hackhaslam]

This broke recently. If no proxy is detected, the URL remains unset but it still gets into gitno_connection_data_from_url which has assert(url).

[ethomson]

If there's no proxy detected, we should be returning GIT_ENOTFOUND... 🤔

[hackhaslam]

Then http_connect would have to be taught to ignore GIT_ENOTFOUND and continue connecting anyway. It's not obvious to me that GIT_PROXY_AUTO not detecting a proxy should result in GIT_ENOTFOUND, but I can change it along those lines if you think it makes more sense.

[ethomson]

Right - I was reading git_remote__get_http_proxy too quickly and missed the part where we clear the error when the proxy environment variable is not found.

Sorry about that, indeed I agree with your reasoning here.

I worry that the test is a bit hidden though and I might miss this when I revisit this code to add support for proxies over SSL. What about breaking it into its own test:

		if ((error = git_remote__get_http_proxy(t->owner->owner,
			    !!t->server.url.use_ssl, &t->proxy_url)) < 0)
				return error;

		if (!t->proxy_url)
				return 0;

[hackhaslam]

Okay, I made that change. I also added the failing test case.

[ethomson]

I also added the failing test case.

💥 Thanks for doing this.