New defaults to bin

[matklad]

So this switches cargo new default from --lib to --bin, as discussed on IRC.

The first two commits are just refactorings, and the last one actually flips the switch. Surprisingly enough, no tests need to be modified it seems!

r? @withoutboats

[ehuss]

Will updating the Cargo book be done separately? It's not clear to me how that is published.

[matklad]

An excellent comment @ehuss!

I've updated the docs to mention both --bin and --lib. I think it's better to pass an explicit argument in the docs at least for some time, because there may be older Cargos in packages managers and such.

I am almost sure that this is not the only one place in the docs which needs to be updated though :(

Let's cc @steveklabnik just in case :)

[ehuss]

I think src/doc/src/guide/creating-a-new-project.md also needs to be updated, since it talks about --bin in more detail.

[withoutboats]

cc @rust-lang/cargo

Big +1 on this change, I'd like to get it in the same beta as the other change to cargo new, but I know we cut a beta soon so maybe the other change should be held back.

We should be very proactive about announcing this change. Not only do our docs need to change, we also need to inform other people who may be teaching Rust of the change to the default behavior, since they'll likely be walking people through this as a first step.

[withoutboats]

@bors r+

2:50 AM <matklad> 6 weeks seem plenty to me for this change: it seems *much*
less troublesome than the recent CWD change, for example
2:50 AM <matklad> and reverting that `rust-` change to make sure it goes in the
same release as `new --bin` seems like a hassle :)  

[bors]

📌 Commit 9cb10e6 has been approved by withoutboats

[bors]

⌛ Testing commit 9cb10e6 with merge 1780cdf6436f1567bbb90cb9337b6af73643dba3...

[bors]

💡 This pull request was already approved, no need to approve it again.

• This pull request is currently being tested. If there's no response from the continuous integration service, you may use retry to trigger a build again.

[bors]

📌 Commit 9cb10e6 has been approved by withoutboats

[bors]

⌛ Testing commit 9cb10e6 with merge 7320c305e981f24e7fa3cb2d07ce58358256ca8d...

[bors]

💡 This pull request was already approved, no need to approve it again.

• This pull request is currently being tested. If there's no response from the continuous integration service, you may use retry to trigger a build again.

[bors]

📌 Commit 9cb10e6 has been approved by withoutboats

[bors]

⌛ Testing commit 9cb10e6 with merge 5891aec...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: withoutboats
Pushing 5891aec to master...

[pwoolcoc]

@matklad got here from TWIR, I was wondering if the reasoning was recorded anywhere other than IRC? I'm just curious what the reasoning was.

[matklad]

@pwoolcoc sure, #5013 (comment) I believe is the most recent discussion (it includes the link to urlo post as well).

The TL;DR is

• new users want --bin for hello world.
• some old users (for example @matklad) create a dozen of crates per day just for experimentation, and for experiments --bin makes more sense.

[pwoolcoc]

@matklad thanks!

[ramn]

What do you think about allowing cargo bin and cargo lib? Silly proof of concept: https://crates.io/crates/cargo-bin-lib

You know what you will get and with less typing to boot.