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/secondary/setup.go

@@ -0,0 +1,108 @@
+package secondary
+
+import (
+	"github.com/coredns/coredns/core/dnsserver"
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/file"
+	"github.com/coredns/coredns/plugin/pkg/dnsutil"
+	"github.com/coredns/coredns/plugin/proxy"
+
+	"github.com/mholt/caddy"
+)
+
+func init() {
+	caddy.RegisterPlugin("secondary", caddy.Plugin{
+		ServerType: "dns",
+		Action:     setup,
+	})
+}
+
+func setup(c *caddy.Controller) error {
+	zones, err := secondaryParse(c)
+	if err != nil {
+		return plugin.Error("secondary", err)
+	}
+
+	// Add startup functions to retrieve the zone and keep it up to date.
+	for _, n := range zones.Names {
+		z := zones.Z[n]
+		if len(z.TransferFrom) > 0 {
+			c.OnStartup(func() error {
+				z.StartupOnce.Do(func() {
+					z.TransferIn()
+					go func() {
+						z.Update()
+					}()
+				})
+				return nil
+			})
+		}
+	}
+
+	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
+		return Secondary{file.File{Next: next, Zones: zones}}
+	})
+
+	return nil
+}
+
+func secondaryParse(c *caddy.Controller) (file.Zones, error) {
+	z := make(map[string]*file.Zone)
+	names := []string{}
+	origins := []string{}
+	prxy := proxy.Proxy{}
+	for c.Next() {
+
+		if c.Val() == "secondary" {
+			// secondary [origin]
+			origins = make([]string, len(c.ServerBlockKeys))
+			copy(origins, c.ServerBlockKeys)
+			args := c.RemainingArgs()
+			if len(args) > 0 {
+				origins = args
+			}
+			for i := range origins {
+				origins[i] = plugin.Host(origins[i]).Normalize()
+				z[origins[i]] = file.NewZone(origins[i], "stdin")
+				names = append(names, origins[i])
+			}
+
+			for c.NextBlock() {
+
+				t, f := []string{}, []string{}
+				var e error
+
+				switch c.Val() {
+				case "transfer":
+					t, f, e = file.TransferParse(c, true)
+					if e != nil {
+						return file.Zones{}, e
+					}
+				case "upstream":
+					args := c.RemainingArgs()
+					if len(args) == 0 {
+						return file.Zones{}, c.ArgErr()
+					}
+					ups, err := dnsutil.ParseHostPortOrFile(args...)
+					if err != nil {
+						return file.Zones{}, err
+					}
+					prxy = proxy.NewLookup(ups)
+				default:
+					return file.Zones{}, c.Errf("unknown property '%s'", c.Val())
+				}
+
+				for _, origin := range origins {
+					if t != nil {
+						z[origin].TransferTo = append(z[origin].TransferTo, t...)
+					}
+					if f != nil {
+						z[origin].TransferFrom = append(z[origin].TransferFrom, f...)
+					}
+					z[origin].Proxy = prxy
+				}
+			}
+		}
+	}
+	return file.Zones{Z: z, Names: names}, nil
+}