git: update gitutil test utilities

- Adds a new GitServeHTTP function to start an http server to serve a
  target git repository.
- Adds a new GitDir helper method to get the path to the .git
  directory
- Updates the GitAdd method to take a variable number of files

Signed-off-by: Justin Chadwell <me@jedevc.com>

util/gitutil/testutilserve.go

@@ -0,0 +1,62 @@
+package gitutil
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func GitServeHTTP(c *Git, t testing.TB) (url string) {
+	t.Helper()
+	gitUpdateServerInfo(c, t)
+	ctx, cancel := context.WithCancel(context.TODO())
+
+	ready := make(chan struct{})
+	done := make(chan struct{})
+
+	name := "test.git"
+	dir, err := c.GitDir()
+	if err != nil {
+		cancel()
+	}
+
+	var addr string
+	go func() {
+		mux := http.NewServeMux()
+		prefix := fmt.Sprintf("/%s/", name)
+		mux.Handle(prefix, http.StripPrefix(prefix, http.FileServer(http.Dir(dir))))
+		l, err := net.Listen("tcp", "localhost:0")
+		if err != nil {
+			panic(err)
+		}
+
+		addr = l.Addr().String()
+
+		close(ready)
+
+		s := http.Server{Handler: mux} //nolint:gosec // potential attacks are not relevant for tests
+		go s.Serve(l)
+		<-ctx.Done()
+		s.Shutdown(context.TODO())
+		l.Close()
+
+		close(done)
+	}()
+	<-ready
+
+	t.Cleanup(func() {
+		cancel()
+		<-done
+	})
+	return fmt.Sprintf("http://%s/%s", addr, name)
+}
+
+func gitUpdateServerInfo(c *Git, tb testing.TB) {
+	tb.Helper()
+	_, err := fakeGit(c, "update-server-info")
+	require.NoError(tb, err)
+}