estimate: fix for modules that don't have a root package

Some modules don't have any .go files in their root directory (e.g.
github.com/autobrr/qui), which means they have no root package. This
led to the error "no required module provides package foo" when trying
to list the direct dependencies of the estimated module.

To fix this, we now make sure to use "go list" in module mode using
the "-m" option when looking for the module directory in the GOPATH.

Author: n-peugnet

estimate.go

@@ -88,7 +88,7 @@ func get(gopath, repodir, repo, rev string) error {
 // getModuleDir returns the path of the directory containing a module for the
 // given GOPATH and repository dir values.
 func getModuleDir(gopath, repodir, module string) (string, error) {
-	cmd := exec.Command("go", "list", "-f", "{{.Dir}}", module)
+	cmd := exec.Command("go", "list", "-m", "-f", "{{.Dir}}", module)
 	cmd.Dir = repodir
 	cmd.Stderr = os.Stderr
 	cmd.Env = append([]string{