Auto merge of #4155 - ketralnis:fossil, r=alexcrichton
Add fossil VCS support to `cargo new`
Fossil is a simple, high-reliability, distributed software configuration management system <https://www.fossil-scm.org/>
I mostly followed https://github.com/rust-lang/cargo/pull/3842 as a template. Like that one, this only adds support for `cargo new`, not for pulling down fossil-hosted dependencies
A problem that i didn't tackle but I'd be willing to is a little more more `trait`ifying of the VCSs. I would need some guidance on that since it looks like git has some more thorough support than e.g. hg does but it looks pretty doable
projects / cargo.git / commit