Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/auto/watcher_test.go

@@ -0,0 +1,58 @@
+package auto
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"path"
+	"regexp"
+	"testing"
+)
+
+func TestWatcher(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+
+	tempdir, err := createFiles()
+	if err != nil {
+		if tempdir != "" {
+			os.RemoveAll(tempdir)
+		}
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tempdir)
+
+	ldr := loader{
+		directory: tempdir,
+		re:        regexp.MustCompile(`db\.(.*)`),
+		template:  `${1}`,
+	}
+
+	a := Auto{
+		loader: ldr,
+		Zones:  &Zones{},
+	}
+
+	a.Walk()
+
+	// example.org and example.com should exist
+	if x := len(a.Zones.Z["example.org."].All()); x != 4 {
+		t.Fatalf("Expected 4 RRs, got %d", x)
+	}
+	if x := len(a.Zones.Z["example.com."].All()); x != 4 {
+		t.Fatalf("Expected 4 RRs, got %d", x)
+	}
+
+	// Now remove one file, rescan and see if it's gone.
+	if err := os.Remove(path.Join(tempdir, "db.example.com")); err != nil {
+		t.Fatal(err)
+	}
+
+	a.Walk()
+
+	if _, ok := a.Zones.Z["example.com."]; ok {
+		t.Errorf("Expected %q to be gone.", "example.com.")
+	}
+	if _, ok := a.Zones.Z["example.org."]; !ok {
+		t.Errorf("Expected %q to still be there.", "example.org.")
+	}
+}