Failure to load dependencies with long file names on Windows

[naim94a]

Problem

When trying to build a crate on Windows that has dependencies with long file names, cargo fails to pull dependencies with a "path too long" error. This issue does not seem to appear on Linux (tested with WSL).

The output I got from cargo build

error: failed to load source for a dependency on `curve25519-fiat`

Caused by:
  Unable to update https://github.com/calibra/rust-curve25519-fiat.git#d7e30233

Caused by:
  failed to update submodule `fiat-crypto`

Caused by:
  failed to update submodule `coqprime`

Caused by:
  invalid path '\\?\C:\Users\User\.cargo\git\checkouts\rust-curve25519-fiat-d934e46b8646fad1\d7e3023\curve25519-fiat\src\external\fiat-crypto\coqprime\src\Coqprime\examples\prime216656403549020227250327256032933021325435259861468456540459488823774358486649614451547405419273433458932168893949521787.v' (path too long); class=Filesystem (30)

Steps

1. git clone https://github.com/libra/libra.git
2. cargo build

Possible Solution(s)

• I assume this issue is related to this bug that exists in libgit2 since 2015: Support core.longpaths on Windows libgit2/libgit2#3053. If so, pushing for a fix in libgit2 may resolve this issue.
• Make cargo use the system's git command, or add an option to use another binary instead of libgit2.

Notes
Output of cargo version:
cargo 1.37.0-nightly (4c1fa54 2019-06-24)

As of today, libra is locked on rust nightly-2019-07-08.

[alexcrichton]

While still a bug in this crate, if you're getting this as an error through Cargo you can try using Cargo's git-fetch-with-cli option:

[net]
git-fetch-with-cli = true

[ehuss]

I don't think git-fetch-with-cli helps because cargo still uses libgit2 to read/extract the repo, and it fails (at least in my testing).

[naim94a]

I can confirm that adding git-fetch-with-cli doesn't fix the problem

[ehuss]

I'm going to close this as a duplicate of #13020, even though this is older, that has more information.