Cargo always hits the network in this patch.crates-io setup

[rukai]

With a cargo.toml like:

[package]
name = "foo"
version = "0.1.0"

[dependencies]
vulkano = { version = "0.7" }
vulkano_text = { version = "0.6" }

[patch.crates-io]
vulkano = { git = "https://github.com/rukai/vulkano", branch = "pf_sandbox" }
vulkano_text = { git = "https://github.com/rukai/vulkano-text", branch = "pf_sandbox" }

Running cargo run && cargo run --frozen gives:

    Updating registry `https://github.com/rust-lang/crates.io-index`
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running `target/debug/foo`
Hello world!
error: failed to load source for a dependency on `vulkano`

Caused by:
  Unable to update registry `https://github.com/rust-lang/crates.io-index`

Caused by:
  attempting to make an HTTP request, but --frozen was specified

[alexcrichton]

Thanks for the report and the detailed test case! I've managed to create a minimal reproduction and narrow down the issue, I'll look into fixing this tomorrow.

[alexcrichton]

Ok added a fix at #4949