Track which commands a registry supports in its config.json

[withoutboats]

This arose out of #4574. The idea is for cargo to only perform an action if the registry supports that command.

The 5 existing commands that interact with registries are:

1. publish
2. yank
3. owner
4. search
5. login (technically never makes a direct request, but is clearly an interaction with the registry semantically)

This proposes to track each command as an array of supported versions:

{
    "api": "https://crates.io/",
    "dl": "https://crates.io/api/v1/crates",
    "commands": {
        "publish": ["v1"],
        "yank": ["v1"],
        "owner": ["v1"],
        "search": ["v1"],
        "login": ["v1"]
    }
}

(On the issue it was discussed having an "api" string for each command, but the actual APIs of the commands are not conducive to this because parts of the query are in the path.)

Before merging, this commands object would need to be added to the config.json of the crates.io index.

@cswindle @carols10cents @rust-lang/cargo

[rust-highfive]

r? @alexcrichton

(rust_highfive has picked a reviewer for you, use r? to override)

[alexcrichton]

This seems reasonable to me! (although I haven't really spent much time thinking through ramifications. I think merging of this would need to be preceded with a change to the actual index, right?

[withoutboats]

I think merging of this would need to be preceded with a change to the actual index, right?

Correct

[withoutboats]

Can't replicate the test failure locally :-\

[alexcrichton]

Hm using the latest stable locally on a fresh checkout if I do

$ cargo test --test lockfile-compat frozen
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running target/debug/deps/lockfile_compat-7dabde45d28ef23c

running 1 test
test frozen_flag_preserves_old_lockfile ... FAILED

failures:

---- frozen_flag_preserves_old_lockfile stdout ----
        running `/home/alex/code/cargo/target/debug/cargo build --locked`
thread 'frozen_flag_preserves_old_lockfile' panicked at '
Expected: execs
    but: exited with exit code: 101
--- stdout

--- stderr
    Updating registry `file:///home/alex/code/cargo/target/cit/t0/registry`
error: checksum for `foo v0.1.0` changed between lock files

this could be indicative of a few possible errors:

    * the lock file is corrupt
    * a replacement source in use (e.g. a mirror) returned a different checksum
    * the source itself may be corrupt in one way or another

unable to verify that `foo v0.1.0` is the same as when the lockfile was generated

', /home/alex/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/hamcrest-0.1.1/src/core.rs:31:12
note: Run with `RUST_BACKTRACE=1` for a backtrace.


failures:
    frozen_flag_preserves_old_lockfile

test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 8 filtered out

@matklad mind helping take a look at this failure (it's on master, not just with this PR)

[bors]

☔ The latest upstream changes (presumably #4836) made this pull request unmergeable. Please resolve the merge conflicts.

[alexcrichton]

This has been inactive for some time now so I'm going to close this, but it can of course be resubmitted!