Update resolver to handle endpoint configuration

Adds support for registry mirrors
Adds support for multiple pull endpoints
Adds capabilities to limit trust in public mirrors
Fixes user agent header missing


Signed-off-by: Derek McGowan <derek@mcgstyle.net>

remotes/docker/registry_test.go

@@ -0,0 +1,76 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package docker
+
+import "testing"
+
+func TestHasCapability(t *testing.T) {
+	var (
+		pull = HostCapabilityPull
+		rslv = HostCapabilityResolve
+		push = HostCapabilityPush
+		all  = pull | rslv | push
+	)
+	for i, tc := range []struct {
+		c HostCapabilities
+		t HostCapabilities
+		e bool
+	}{
+		{all, pull, true},
+		{all, pull | rslv, true},
+		{all, pull | push, true},
+		{all, all, true},
+		{pull, all, false},
+		{pull, push, false},
+		{rslv, pull, false},
+		{pull | rslv, push, false},
+		{pull | rslv, rslv, true},
+	} {
+		if a := tc.c.Has(tc.t); a != tc.e {
+			t.Fatalf("%d: failed, expected %t, got %t", i, tc.e, a)
+		}
+	}
+}
+
+func TestMatchLocalhost(t *testing.T) {
+	for _, tc := range []struct {
+		host  string
+		match bool
+	}{
+		{"", false},
+		{"127.1.1.1", false},
+		{"127.0.0.1", true},
+		{"127.0.0.1:5000", true},
+		{"registry.org", false},
+		{"localhost", true},
+		{"localhost:5000", true},
+		{"[127:0:0:1]", false},
+		{"[::1]", true},
+		{"[::1]:5000", true},
+		{"::1", true},
+	} {
+		actual, _ := MatchLocalhost(tc.host)
+		if actual != tc.match {
+			if tc.match {
+				t.Logf("Expected match for %s", tc.host)
+			} else {
+				t.Logf("Unexpected match for %s", tc.host)
+			}
+			t.Fail()
+		}
+	}
+}