List directories being watched when server is run

Fixes part of issue 1030. Previously hugo only listed the content
directory as being watched. Now we list all files being watched
according to `commands.getDirList()`. We also introduce a RemoveSubpaths
function and test in the helpers module to reduce noise in the command
line output by not showing subdirectories of ones already being watched.

For example, instead of:
`Watching for changes in $HOME/blog/content`
We get:
`Watching for changes in
$HOME/blog/{data,content,layouts,static,themes/my-theme}`

commands/server.go

@@ -98,7 +98,14 @@ func server(cmd *cobra.Command, args []string) {
 
 	// Watch runs its own server as part of the routine
 	if serverWatch {
-		jww.FEEDBACK.Println("Watching for changes in", helpers.AbsPathify(viper.GetString("ContentDir")))
+		watched := getDirList()
+		workingDir := helpers.AbsPathify(viper.GetString("WorkingDir"))
+		for i, dir := range watched {
+			watched[i], _ = helpers.GetRelativePath(dir, workingDir)
+		}
+		unique := strings.Join(helpers.RemoveSubpaths(watched), ",")
+
+		jww.FEEDBACK.Printf("Watching for changes in %s/{%s}\n", workingDir, unique)
 		err := NewWatcher(serverPort)
 		if err != nil {
 			fmt.Println(err)

helpers/path.go

@@ -365,6 +365,39 @@ func PrettiyPath(in string, b FilepathPathBridge) string {
 	return b.Join(b.Dir(in), name, "index"+ext)
 }
 
+// RemoveSubpaths takes a list of paths and removes everything that
+// contains another path in the list as a prefix. Ignores any empty
+// strings. Used mostly for logging.
+//
+// e.g. ["hello/world", "hello", "foo/bar", ""] -> ["hello", "foo/bar"]
+func RemoveSubpaths(paths []string) []string {
+	a := make([]string, 0)
+	for _, cur := range paths {
+		// ignore trivial case
+		if cur == "" {
+			continue
+		}
+
+		isDupe := false
+		for i, old := range a {
+			if strings.HasPrefix(cur, old) {
+				isDupe = true
+				break
+			} else if strings.HasPrefix(old, cur) {
+				a[i] = cur
+				isDupe = true
+				break
+			}
+		}
+
+		if !isDupe {
+			a = append(a, cur)
+		}
+	}
+
+	return a
+}
+
 // FindCWD returns the current working directory from where the Hugo
 // executable is run.
 func FindCWD() (string, error) {

helpers/path_test.go

@@ -2,10 +2,10 @@ package helpers
 
 import (
 	"fmt"
-	"github.com/spf13/viper"
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"strconv"
 	"strings"
@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/spf13/afero"
+	"github.com/spf13/viper"
 )
 
 func TestMakePath(t *testing.T) {
@@ -545,6 +546,14 @@ func TestPrettifyPath(t *testing.T) {
 
 }
 
+func TestRemoveSubpaths(t *testing.T) {
+	got := RemoveSubpaths([]string{"hello", "hello/world", "foo/bar", ""})
+	expect := []string{"hello", "foo/bar"}
+	if !reflect.DeepEqual(got, expect) {
+		t.Errorf("Test %d failed. Expected %q but got %q", expect, got)
+	}
+}
+
 func TestFindCWD(t *testing.T) {
 	type test struct {
 		expectedDir string