Vendor sources into separate directories

[ljli]

I thought #59 could be addressed by keeping sources in separate directories and replacing them 1-to-1, instead of replacing all sources with a single merged source.
It seems to work so far. Currently it breaks most of the tests, if this is the way to go I'll fix the tests, incorporate any feedback and update the PR.

[alexcrichton]

Thanks for the PR! I wonder if perhaps we could still put everything into a vendor folder, but subfolders could be used for non-crates-io sources? Something like vendor/git-$host-$hash/$krate or something like that?

[ljli]

The scheme of this PR is vendor/${source-hash}/$krate. You propose to remove the ${source-hash} component for crates.io crates and to make it less opaque for non-crates.io crates by adding the source type and the host part of the url, right? I think that should work, too. The $host part will probably be git{hub,lab,...}.com most of the time, but still more info than before.

[alexcrichton]

Ah ok, I just think we by default want to stick with mostly the same layout as we have today to avoid lots of churn in vendored repos. This could also be behind a flag though to prevent that!

[ljli]

I updated the PR. It is possible to get the old behavior with the flag --merge-sources. The vendor folder structure looks like this vendor/{git,registry}-${source-hash}/$crate. It is no problem to switch between having --merge-sources and not having it, but nothing clever happens, the vendor folder is just deleted and repopulated.
The .cargo/config file that gets printed looks like this now:

[source.crates-io]
replace-with = "vendor+crates-io"

[source."https://github.com/rust-lang/libc"]
git = "https://github.com/rust-lang/libc"
rev = "add1a320b4e1b454794a034e3f4218f877c393fc"
replace-with = "vendor+https://github.com/rust-lang/libc"

[source."vendor+crates-io"]
directory = "/home/me/devel/cargo-vendor/target/tmp/test0/vendor/registry-40351f815f426200"

[source."vendor+https://github.com/rust-lang/libc"]
directory = "/home/me/devel/cargo-vendor/target/tmp/test0/vendor/git-4d8ca19d6a651200"

I made the new behavior the default for now, but I don't have a strong opinion on this and no insight into how many users checked vendor folders into version control, if you want another default I'll change it.

[alexcrichton]

Thanks! Could the old behavior be left as the default though? Perhaps a --no-merge-sources option instead? Could the README also document the flag and why it would be used?

[ljli]

Could the old behavior be left as the default though? Perhaps a --no-merge-sources option instead?

Done

Could the README also document the flag and why it would be used?

Done

[alexcrichton]

Thanks!