The fetch package is used in the project https://github.com/chainguard-dev/apko/ to fetch packages and dependencies. It is a Go package that provides functions to fetch resources from git repositories.
The main function in the fetch package is Fetch(path string) ([]byte, error). This function takes a path as input, which can be a git repository reference, and returns the contents of the repository at that reference and any potential error. It does this by creating a temporary directory, cloning the git repository into that directory, checking out the specified reference, and then reading the contents of the requested file or directory.
Here’s an example of how to use the Fetch function to get the contents of a file in a git repository:
data, err := fetch.Fetch("https://github.com/chainguard-dev/apko@main")
if err != nil {
log.Fatalf("failed to fetch repository: %v", err)
}
fmt.Println(string(data))
The fetch package also provides a resource struct, which is used to represent a resource in a git repository. This struct has four fields: host, repository, path, and reference. The host field is the hostname of the git repository, the repository field is the name of the repository, the path field is the path to the file or directory in the repository, and the reference field is the reference (e.g. branch or tag) to checkout.
Here’s an example of how to use the resource struct to fetch the contents of a file in a git repository:
r := &fetch.Resource{
Host: "github.com",
Repository: "chainguard-dev/apko",
Path: "apko.yaml",
Reference: "main",
}
data, err := fetch.Fetch(r)
if err != nil {
log.Fatalf("failed to fetch repository: %v", err)
}
fmt.Println(string(data))
The fetch package also provides a parseRef function, which takes a path as input and returns a resource struct. This function is used to parse the path and extract the host, repository, path, and reference fields.
Here’s an example of how to use the parseRef function to parse a path and get a resource struct:
r, err := fetch.ParseRef("https://github.com/chainguard-dev/apko@main")
if err != nil {
log.Fatalf("failed to parse git reference: %v", err)
}
fmt.Println(r)
The fetch package uses the go-git package to interact with git repositories. It also uses the net/url package to parse URLs and the path/filepath package to manipulate file paths.
Sources:
