Initial provider implementation (#18)

This brings over the initial buildx prototype from pulumi/pulumi-docker
and fixes various build and release issues.

provider/internal/ssh.go

@@ -0,0 +1,79 @@
+// Copyright 2024, Pulumi Corporation.
+//
+// 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 internal
+
+import (
+	"strings"
+
+	controllerapi "github.com/docker/buildx/controller/pb"
+	"github.com/docker/buildx/util/buildflags"
+
+	"github.com/pulumi/pulumi-go-provider/infer"
+)
+
+// SSH is an SSH option.
+type SSH struct {
+	ID    string   `pulumi:"id"`
+	Paths []string `pulumi:"paths,optional"`
+}
+
+// Annotate sets docstrings on SSH.
+func (s *SSH) Annotate(a infer.Annotator) {
+	a.Describe(&s.ID, dedent(`
+		Useful for distinguishing different servers that are part of the same
+		build.
+
+		A value of "default" is appropriate if only dealing with a single host.
+	`))
+	a.Describe(&s.Paths, dedent(`
+		SSH agent socket or private keys to expose to the build under the given
+		identifier.
+
+		Defaults to "[$SSH_AUTH_SOCK]".
+
+		Note that your keys are **not** automatically added when using an
+		agent. Run "ssh-add -l" locally to confirm which public keys are
+		visible to the agent; these will be exposed to your build.
+	`))
+}
+
+// String returns a CLI-encoded value for the SSH option, or an empty string if
+// its ID is not known.
+func (s SSH) String() string {
+	if s.ID == "" {
+		return ""
+	}
+
+	r := s.ID
+
+	if len(s.Paths) > 0 {
+		r += "=" + strings.Join(s.Paths, ",")
+	}
+
+	return r
+}
+
+func (s SSH) validate() (*controllerapi.SSH, error) {
+	parsed, err := buildflags.ParseSSHSpecs([]string{s.String()})
+	if err != nil {
+		return nil, err
+	}
+	if len(parsed) == 0 {
+		return nil, nil
+	}
+
+	_, err = controllerapi.CreateSSH([]*controllerapi.SSH{{ID: s.ID, Paths: s.Paths}})
+	return parsed[0], err
+}