Fix Julia LoadError: Failed To Clone Private Repo

Hey guys! Ever run into that super frustrating LoadError: failed to clone from ***, error: GitError(Code:EUSER, Class:Callback, Aborting, user cancelled credential request.) when trying to benchmark a private repository with AirspeedVelocity.jl? Yeah, it's a real pain. You've probably tried following the instructions, maybe even tweaked some settings, but that stubborn error message just keeps popping up, asking for your username and password. Don't sweat it, we've all been there! This common hiccup usually means that Julia's package manager, Pkg, is struggling to authenticate with your private Git repository. It's like trying to get into a secret club without the right handshake. The good news is that this is often solvable, and today we're going to break down why this happens and how you can get past it, ensuring your benchmarking journey with AirspeedVelocity.jl is smooth sailing.

We'll dive deep into the common causes, explore potential solutions, and discuss why sometimes switching to SSH might be the golden ticket. The error itself, user cancelled credential request, is a pretty big hint. It suggests that the system is trying to ask for credentials, but for some reason, it's not able to get them from you or the usual authentication mechanisms. This could be due to a few reasons: maybe your Git credentials aren't configured correctly for the command-line tools Julia is using, or perhaps the environment where you're running this (like a CI/CD pipeline) doesn't have the necessary authentication setup. We'll cover how to ensure your local Git setup is talking nicely with Julia and explore alternative authentication methods that might bypass this roadblock entirely. So, grab your favorite beverage, and let's get this problem sorted!

Understanding the GitError(Code:EUSER, Class:Callback)

Alright, let's get a bit technical for a sec, but don't worry, we'll keep it light! That GitError(Code:EUSER, Class:Callback, Aborting, user cancelled credential request.) message is your cue that Git, the version control system Julia's Pkg is using under the hood, is running into trouble authenticating. When you try to add a package from a private repository, Pkg needs to clone that repository to your local machine. To do this, it uses Git. If the repository is private, Git needs to verify your identity, usually through a username and password, or via SSH keys. The EUSER code generally points to a user-related issue, and the Callback class with the message user cancelled credential request specifically means that Git tried to prompt for credentials (like asking for your username and password), but the process was somehow cancelled or failed. This is why you see that prompt Username for 'https://github.com/': appear and then immediately fail.

Several things can cause this cancellation. One common culprit is how your system handles Git credentials. If you're using HTTPS to clone, Git often relies on a credential helper to store and provide your username and password. If this helper isn't configured correctly, or if it's not running in the environment you're executing the Julia code, Git won't be able to retrieve your credentials. This is especially true in automated environments like GitHub Actions or other CI/CD pipelines, where interactive prompts are simply not possible and a non-interactive authentication method is required. The error user cancelled credential request is precisely what happens when an interactive prompt is expected but cannot be fulfilled. The system essentially says, "I tried to ask the user for credentials, but that didn't work out," leading to the abort.

Another reason might be related to the specific settings within the project you're trying to use, like AirspeedVelocity.jl. While the issue you linked provides some good starting points, sometimes the way a package manager or a specific tool interacts with Git can have its own nuances. It's possible that the default Pkg behavior or AirspeedVelocity's specific implementation of fetching repositories isn't perfectly aligned with your current Git configuration or the security protocols in place. This is why exploring alternative methods, such as SSH, becomes a viable and often more robust solution, especially for private repositories. We'll delve into these solutions next, so hang tight!

Troubleshooting Steps: From HTTPS to SSH

Okay, so we know the problem is authentication. Let's roll up our sleeves and try some fixes! The most common approach is to ensure your Git credentials are set up correctly for HTTPS, but if that doesn't pan out, switching to SSH keys is often the most robust and secure solution for private repositories.

1. Ensure Your Git Credentials Are Set Up (HTTPS)

First things first, let's make sure your local Git is happy. Open your terminal (not the Julia REPL!) and try cloning the repository manually:

git clone <your-private-repo-url>

If Git prompts you for a username and password and it works, then your system's Git is configured. If it fails here too, you might need to set up a Git credential helper. For example, on macOS, you can use the OS's keychain:

git config --global credential.helper osxkeychain

On Linux, you might use libsecret or gnome-keyring. On Windows, Git Credential Manager is usually the go-to.

Even with a helper, sometimes Julia's Pkg might not pick it up correctly. The previous link you shared mentions setting GIT_TERMINAL_PROMPT=0. While this is meant to disable interactive prompts (useful in CI), it might sometimes interfere with how credentials are passed if not set up perfectly. Double-check any environment variables you've set related to Git or your Julia environment.

2. The SSH Solution: A More Secure and Reliable Path

For private repositories, using SSH keys is generally the preferred method. It's more secure because you're not transmitting your username and password over the network, and it often simplifies authentication, especially in automated environments. Here’s how to set it up:

• Generate an SSH Key Pair: If you don't have one, generate a new SSH key pair. Open your terminal and run:

  ssh-keygen -t ed25519 -C "your_email@example.com"
  

  Follow the prompts. It's a good idea to set a passphrase for extra security.

• Add the Public Key to Your Git Provider: Copy the contents of your public key (usually ~/.ssh/id_ed25519.pub or ~/.ssh/id_rsa.pub). Then, go to your GitHub (or GitLab, Bitbucket, etc.) account settings, navigate to