Support specifying API location everywhere rather than requiring specifying index location

[carols10cents]

@alexcrichton has expressed interest in this in places like this comment and I agree:

Ok but to be clear we don't even know what the "url of a registry" is today. The url we currently use in lots of places, the index, seems clearly inferior to the actual url like "https://crates.io".

Basically I don't think we should have to specify the location of an index anywhere ever, including within cargo's code, we should only ever have to specify the URL of the API server and that API should know where to find its index.

[fa7ca7]

I can't understand. This issue supposes to change index->host. #4209 changes host->index in publish subcommand. Could please someone explain why it has been merged?

[fa7ca7]

bin/search has the same mess with host/index as bin/publish.

[carols10cents]

I can't understand. This issue supposes to change index->host. #4209 changes host->index in publish subcommand. Could please someone explain why it has been merged?

#4209 changes the name of the argument; previously the argument was named host but needed the location of an index to work at all.

This issue is to actually take a host instead of an index location, everywhere, and the functionality of cargo and crates.io will need to be changed in order to close this issue.

Does that clear it up?

Please file a new issue for bin/search, thanks!

[fa7ca7]

Ah got it! Thank you for clarification.
Filed an issue #4219.

[ashleygwilliams]

notes from chatting with @carols10cents:

• needs to be done in a backwards compatible way
• need to figure out the set of all things this touches
• required for supporting multiple registries
• host appears to have been (semi?)deprecated for index, so we need to wait a cycle to repurpose host for this (hence marking as scheduled change)