`cargo new` creates a weird _git2 symlink

[akatechis]

Problem
I'm not sure if it's even a bug, but I am running on Windows 10 Pro. I use Git Bash, as my "terminal", and when I create a new rust binary project, along with all the expected files/directories, I get what looks like a weird link file to some sort of testing file/dir.

If I try to open that link as a directory, I get an error that it doesn't exist. Is this some temporary working directory that is not being cleaned up?

Steps
With the below versions of cargo/git, issue the following commands:

1. cargo new foo.
2. cd foo
3. ls -l

Notes
Here's the relevant transcript of commands indicating what I see, and the versions of relevant tools:

$ cargo --version
cargo 1.37.0-nightly (4c1fa54d1 2019-06-24)

$ rustc --version
rustc 1.37.0-nightly (0af8e872e 2019-06-30)

$ rustup --version
rustup 1.18.3 (435397f48 2019-05-22)

$ ll
total 18
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 09:57 ./
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 09:56 ../
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 09:56 .git/
-rw-r--r-- 1 alex.katechis 1049089  19 Jul 24 09:56 .gitignore
lrwxrwxrwx 1 alex.katechis 1049089   7 Jul 24 09:56 _git2_a08784 -> testing
-rw-r--r-- 1 alex.katechis 1049089 244 Jul 24 09:56 Cargo.toml
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 09:56 src/

# Then I run `rustup update` to get the latest nightly...

$ ll
total 18
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 10:03 ./
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 10:03 ../
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 10:03 .git/
-rw-r--r-- 1 alex.katechis 1049089  19 Jul 24 10:03 .gitignore
lrwxrwxrwx 1 alex.katechis 1049089   7 Jul 24 10:03 _git2_a02928 -> testing
-rw-r--r-- 1 alex.katechis 1049089 240 Jul 24 10:03 Cargo.toml
drwxr-xr-x 1 alex.katechis 1049089   0 Jul 24 10:03 src/

$ cargo --version
cargo 1.38.0-nightly (e3563dbdc 2019-07-16)

$ rustc --version
rustc 1.38.0-nightly (a7f28678b 2019-07-23)

$ git --version
git version 2.19.0.windows.1

[alexcrichton]

Hm so I've actually been seeing this for quite some time as well but I figured it was some local issue I hadn't figured out yet. I'm in basically the same situation, and this affects the beta channel as well.

I suspect this is tied to the recent update to libgit2, but for some reason this isn't happening on our CI because it causes issues with tests as well... @ehuss do you know if this is perhaps a bug that was fixed recently in libgit2?

[alexcrichton]

Oh nvmd, I also possess the power of searching the internet. Looks like this was a bug in libgit2 (libgit2/libgit2#5147) fixed in libgit2/libgit2#5151

[azureskydiver]

I am still seeing this behavior in version 1.37. I installed rustup-init.exe from the main rust-lang.org site this evening and ran cargo new hello_cargo. A weird "_git2_a22412" directory was created along with the other files and directory described by the Rust book and the cargo manual.

[ehuss]

@azureskydiver We did not backport the fix to 1.37. Honestly, I didn't think about it, and didn't really expect many people to enable core.symlinks. It should be fixed in 1.38 (beta). You can set git's core.symlinks to false, or just delete the directory in the meantime.