install/uninstall: allow aliasing buildx to docker builder

Currently the user can type `docker buildx` to use this tool.
This patch allows the user to install buildx as a `docker builder` alias.

As an additional benefit, this allows the regular `docker build` to hook
into `buildx build`.

Note that the install and uninstall commands are currently hidden.

Signed-off-by: Tibor Vass <tibor@docker.com>

vendor/github.com/docker/cli/cli/command/registry.go

@@ -28,16 +28,22 @@ func ElectAuthServer(ctx context.Context, cli Cli) string {
 	// used. This is essential in cross-platforms environment, where for
 	// example a Linux client might be interacting with a Windows daemon, hence
 	// the default registry URL might be Windows specific.
-	serverAddress := registry.IndexServer
-	if info, err := cli.Client().Info(ctx); err != nil && debug.IsEnabled() {
-		// Only report the warning if we're in debug mode to prevent nagging during engine initialization workflows
-		fmt.Fprintf(cli.Err(), "Warning: failed to get default registry endpoint from daemon (%v). Using system default: %s\n", err, serverAddress)
-	} else if info.IndexServerAddress == "" && debug.IsEnabled() {
-		fmt.Fprintf(cli.Err(), "Warning: Empty registry endpoint from daemon. Using system default: %s\n", serverAddress)
-	} else {
-		serverAddress = info.IndexServerAddress
+	info, err := cli.Client().Info(ctx)
+	if err != nil {
+		// Daemon is not responding so use system default.
+		if debug.IsEnabled() {
+			// Only report the warning if we're in debug mode to prevent nagging during engine initialization workflows
+			fmt.Fprintf(cli.Err(), "Warning: failed to get default registry endpoint from daemon (%v). Using system default: %s\n", err, registry.IndexServer)
+		}
+		return registry.IndexServer
 	}
-	return serverAddress
+	if info.IndexServerAddress == "" {
+		if debug.IsEnabled() {
+			fmt.Fprintf(cli.Err(), "Warning: Empty registry endpoint from daemon. Using system default: %s\n", registry.IndexServer)
+		}
+		return registry.IndexServer
+	}
+	return info.IndexServerAddress
 }
 
 // EncodeAuthToBase64 serializes the auth configuration as JSON base64 payload

vendor/github.com/docker/cli/cli/command/utils.go

@@ -161,3 +161,34 @@ func ValidateOutputPathFileMode(fileMode os.FileMode) error {
 	}
 	return nil
 }
+
+func stringSliceIndex(s, subs []string) int {
+	j := 0
+	if len(subs) > 0 {
+		for i, x := range s {
+			if j < len(subs) && subs[j] == x {
+				j++
+			} else {
+				j = 0
+			}
+			if len(subs) == j {
+				return i + 1 - j
+			}
+		}
+	}
+	return -1
+}
+
+// StringSliceReplaceAt replaces the sub-slice old, with the sub-slice new, in the string
+// slice s, returning a new slice and a boolean indicating if the replacement happened.
+// requireIdx is the index at which old needs to be found at (or -1 to disregard that).
+func StringSliceReplaceAt(s, old, new []string, requireIndex int) ([]string, bool) {
+	idx := stringSliceIndex(s, old)
+	if (requireIndex != -1 && requireIndex != idx) || idx == -1 {
+		return s, false
+	}
+	out := append([]string{}, s[:idx]...)
+	out = append(out, new...)
+	out = append(out, s[idx+len(old):]...)
+	return out, true
+}