Tuesday, March 07, 2017

Serving Git repositories from Go

I have a small web server written in Go.  I wanted to serve Git repositories from this server.  It turned out to be surprisingly easy since git-http-backend and the cgi package do all the hard work.

First, define a function for handling Git's HTTP requests:

func git(w http.ResponseWriter, r *http.Request) {
        username, password, ok := r.BasicAuth()
        if !ok || username != "john" || password != "secret" {
                w.Header().Set("Content-Type", "text/plain")
                w.Header().Set("WWW-Authenticate", "Basic realm=\"example.com git\"")
                w.WriteHeader(http.StatusUnauthorized)
                fmt.Fprintln(w, "Not authorized")
                return
        }

        const gitRoot = "/path/to/git/repositories/"
        h := &cgi.Handler{
                Path: "/usr/lib/git-core/git-http-backend",
                Root: "/git",
                Dir:  gitRoot,
                Env: []string{
                        "GIT_PROJECT_ROOT=" + gitRoot,
                        "GIT_HTTP_EXPORT_ALL=", // we require auth above
                        "REMOTE_USER=" + username,
                },
        }
        h.ServeHTTP(w, r)
}

Second, connect that function to the mux you're already using:

mux.HandleFunc("/git/", git)

Now I can clone from and push to my little Go server.

1 comment:

Michael Hendricks said...

Performing a large "git push" with this setup gives an error like:

error: RPC failed; result=22, HTTP code = 400

That's because Git uses chunked encoding for large uploads but http/cgi doesn't support chunked encoding.

As a workaround, you can run "git config http.postBuffer 2000000" (with a sufficiently large number) before running "git push". That avoids the chunked encoding.