Update README to append stdout to .cargo/config rather than overwrite

[LeonardMH]

The README suggests doing:

cargo vendor > .cargo/config

To automatically set up your cargo config file, but if you already have a cargo config file this will overwrite it. The more user friendly suggestion would be to append to cargo config with:

cargo vendor >> .cargo/config

In the event that .cargo/config does not exist, this works exactly the same as >, but if it does exist, it will ensure it isn't overwritten.

[mcepl]

Well, but will be the resulting multiple times appended .cargo/config syntactically correct?

[LeonardMH]

@mcepl, I believe the answer is yes. Assuming the .cargo/config file was already syntactically valid then appending more syntactically valid TOML should not break anything.

I would also argue that > is no less risky than >> since potentially losing other changes in your .cargo/config would be a more painful experience than the alternative. This would be more inline with the wording output from cargo-vendor itself:

$ cargo vendor
add this to your .cargo/config for this project:

    ...

"add" implies concatenation.

The only bad(1) scenario I can think of would be the case where you run cargo vendor >> .cargo/config multiple times, but why would you do that?

(1): And in this case I don't think it would actually be all that bad, you'd have a messy .cargo/config but the last added dictionary would likely take precedence (at least according to my wild speculation).

[alexcrichton]

This crate is now included natively in Cargo as of rust-lang/cargo#6869 and today's nightly Rust. I'm closing all issues in this repository before I archive the repository, but if you're still interested in seeing this issue fixed then please feel free to file an issue with Cargo itself!