SCP-like URL to ssh conversion is lossy

[weihanglo]

Current behavior 😯

In SCP-like URL, the path git@github.com:rust-lang/cargo.git is home-relative. The path ought to be ~git/rust-lang/cargo.git. However, gix-url@0.35.2 converts git@github.com:rust-lang/cargo.git to ssh://git@github.com/rust-lang/cargo.git, which is lossy (not wrong). That SSH URL is absolute /rust-lang/cargo.git.

Expected behavior 🤔

I don't really know.

git@github.com:rust-lang/cargo.git -> ssh://git@github.com/~/rust-lang/cargo.git seems to be a more correct behavior. However, as I found in rust-lang/cargo#16740 (comment), GitHub doesn't recognize ssh://git@github.com/~/rust-lang/cargo.git (perhaps for security reason to prevent file system traversal?)

Git behavior

Not related to Git. Git doesn't do conversion.

Steps to reproduce 🕹

Run this cargo script cargo +nightly -Zscript script.rs

---cargo
package.edition = "2024"
dependencies.gix-url = "=0.35.2" 
---
fn main() {
    for url in [
        "git@github.com:rust-lang/cargo.git",
        "git@github.com:/rust-lang/cargo.git",
        "git@github.com:~/rust-lang/cargo.git",
        "git@github.com:~git/rust-lang/cargo.git",
        "git@github.com:/~/rust-lang/cargo.git",
        "git@github.com:/~git/rust-lang/cargo.git",
    ] {
        print(url);
        eprintln!();
    }
}

fn print(url: &str) {
    let scp = gix_url::parse(url.into()).unwrap();
    let canonical = scp.clone().serialize_alternate_form(false).to_bstring();
    eprintln!("SCP-like: {url}");
    eprintln!("path:     {}", std::str::from_utf8(&scp.path).unwrap());
    eprintln!("SSH URL:  {}", std::str::from_utf8(&canonical).unwrap());
}

Output:

SCP-like: git@github.com:rust-lang/cargo.git
path:     rust-lang/cargo.git
SSH URL:  ssh://git@github.com/rust-lang/cargo.git

SCP-like: git@github.com:/rust-lang/cargo.git
path:     /rust-lang/cargo.git
SSH URL:  ssh://git@github.com/rust-lang/cargo.git

SCP-like: git@github.com:~/rust-lang/cargo.git
path:     ~/rust-lang/cargo.git
SSH URL:  ssh://git@github.com/~/rust-lang/cargo.git

SCP-like: git@github.com:~git/rust-lang/cargo.git
path:     ~git/rust-lang/cargo.git
SSH URL:  ssh://git@github.com/~git/rust-lang/cargo.git

SCP-like: git@github.com:/~/rust-lang/cargo.git
path:     ~/rust-lang/cargo.git
SSH URL:  ssh://git@github.com/~/rust-lang/cargo.git

SCP-like: git@github.com:/~git/rust-lang/cargo.git
path:     ~git/rust-lang/cargo.git
SSH URL:  ssh://git@github.com/~git/rust-lang/cargo.git