Support subdir in baseurl.

Mainly this was a change to helpers.MakePermalink, but to get the local server to run correctly,
we needed to redirect the path of the request from /foo to /.  In addition, I added tests for the
server's code for fixing up the base url with different config file & CLI options.

commands/server_test.go

@@ -0,0 +1,42 @@
+package commands
+
+import (
+	"testing"
+
+	"github.com/spf13/viper"
+)
+
+func TestFixUrl(t *testing.T) {
+	type data struct {
+		TestName   string
+		CliBaseUrl string
+		CfgBaseUrl string
+		AppendPort bool
+		Port       int
+		Result     string
+	}
+	tests := []data{
+		{"Basic localhost", "", "http://foo.com", true, 1313, "http://localhost:1313"},
+		{"Basic subdir", "", "http://foo.com/bar", true, 1313, "http://localhost:1313/bar"},
+		{"Basic production", "http://foo.com", "http://foo.com", false, 80, "http://foo.com"},
+		{"Production subdir", "http://foo.com/bar", "http://foo.com/bar", false, 80, "http://foo.com/bar"},
+		{"No http", "", "foo.com", true, 1313, "http://localhost:1313"},
+		{"Override configured port", "", "foo.com:2020", true, 1313, "http://localhost:1313"},
+		{"No http production", "foo.com", "foo.com", false, 80, "http://foo.com"},
+		{"No http production with port", "foo.com", "foo.com", true, 2020, "http://foo.com:2020"},
+	}
+
+	for i, test := range tests {
+		BaseUrl = test.CliBaseUrl
+		viper.Set("BaseUrl", test.CfgBaseUrl)
+		serverAppend = test.AppendPort
+		serverPort = test.Port
+		result, err := fixUrl(BaseUrl)
+		if err != nil {
+			t.Errorf("Test #%d %s: unexpected error %s", err)
+		}
+		if result != test.Result {
+			t.Errorf("Test #%d %s: expected %q, got %q", i, test.TestName, test.Result, result)
+		}
+	}
+}