Allow the use of alternative registry names in [patch]

[sfackler]

If you have an alternative registry configured and want to patch a crate in it, you currently have to spell out the entire URL:

.cargo/config

[registries.foobar]
index = "https://foobar.com/some-long-url/index"

Cargo.toml

...

[dependencies]
thingy = { version = "0.1", registry = "foobar" }

[patch."https://foobar.com/some-long-url/index"]
thingy = { git = "https://somewhere-else.com" }

But it's a bit annoying to have to write the whole URL around (and is the only place you're allowed to use the alternative registry URL directly in Cargo.toml). It'd be great if this worked instead:

[patch.foobar]
thingy = { git = "https://somewhere-else.com" }

[stale]

As there hasn't been any activity here in over 6 months I've marked this as stale and if no further activity happens for 7 days I will close it.

I'm a bot so this may be in error! If this issue should remain open, could someone (the author, a team member, or any interested party) please comment to that effect?

The team would be especially grateful if such a comment included details such as:

• Is this still relevant?
• If so, what is blocking it?
• Is it known what could be done to help move this forward?

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[sfackler]

This is still a nice to have - someone just needs to put in the work to implement it.

[dwijnand]

On face value this looks like it's just a simple lookup. If someone were to leave me some mentoring instructions I'd be happy to have take a swing at it.