Improve error message for invalid path dependencies within git dependencies

[NickeZ]

Problem
I add a git dependency on "noise-rust-crypto" which is part of the "noise-rust" repository and cargo doesn't find it.

$ cargo update
    Updating git repository `https://github.com/sopium/noise-rust`
error: failed to load source for a dependency on `noise-rust-crypto`

Caused by:
  Unable to update https://github.com/sopium/noise-rust

Caused by:
  Could not find `Cargo.toml` in `/home/niklas/.cargo/git/checkouts/noise-rust-6131949caf0d2152/dad7f8b/noise`

Steps

1. echo "noise-rust-crypto = {git = "https://github.com/sopium/noise-rust"}" >> Cargo.toml
2. cargo update

Possible Solution(s)

Notes

Output of cargo version:

$ cargo --version
cargo 1.40.0 (bc8e4c8be 2019-11-22)

[ehuss]

It's a poor error message. The issue is that this line references a directory that doesn't exist.

[NickeZ]

Ok so it actually breaks when it fails instead of continue to search. That sounds brittle. I'll make a pr to the repo. Thanks

[ehuss]

Yea, it is supposed to ignore errors like this. It's just an oversight that it doesn't in this particular case (path dependencies require a special code path).

[NickeZ]

I tried to update the issue name to something actionable. Thanks!

[ehuss]

I think this is now resolved by #7784. Bad paths in the git repo are now ignored (unless the package itself is missing).

[aleksator]

I think this is now resolved by #7784. Bad paths in the git repo are now ignored (unless the package itself is missing).

The link in the message points to this issue. Recursion!
The proper PR is probably this one: #7947