Factor bootstrap logic into bootstrap package

This commit factors out the bootstrap logic into a new `bootstrap`
package, while also moving to `go-git-providers` to handle things
around Git providers (e.g. repository creation, deploy key
upsertions).

The `GitProviderBootstrapper` is a superset of the
`PlainGitBootstrapper` that besides `Reconciler` also implements the
`RepositoryReconciler`.

The Git actions rely on an interface, making it easier to support
other implementations than `go-git` at a later moment, to for example
support bootstrapping to Git servers that only support the v2 protocol.

Signed-off-by: Hidde Beydals <hello@hidde.co>

internal/bootstrap/provider/factory.go

@@ -0,0 +1,58 @@
+/*
+Copyright 2021 The Flux 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 provider
+
+import (
+	"fmt"
+
+	"github.com/fluxcd/go-git-providers/github"
+	"github.com/fluxcd/go-git-providers/gitlab"
+	"github.com/fluxcd/go-git-providers/gitprovider"
+)
+
+// BuildGitProvider builds a gitprovider.Client for the provided
+// Config. It returns an error if the Config.Provider
+// is not supported, or if the construction of the client fails.
+func BuildGitProvider(config Config) (gitprovider.Client, error) {
+	var client gitprovider.Client
+	var err error
+	switch config.Provider {
+	case GitProviderGitHub:
+		opts := []github.ClientOption{
+			github.WithOAuth2Token(config.Token),
+		}
+		if config.Hostname != "" {
+			opts = append(opts, github.WithDomain(config.Hostname))
+		}
+		if client, err = github.NewClient(opts...); err != nil {
+			return nil, err
+		}
+	case GitProviderGitLab:
+		opts := []gitlab.ClientOption{
+			gitlab.WithConditionalRequests(true),
+		}
+		if config.Hostname != "" {
+			opts = append(opts, gitlab.WithDomain(config.Hostname))
+		}
+		if client, err = gitlab.NewClient(config.Token, "", opts...); err != nil {
+			return nil, err
+		}
+	default:
+		return nil, fmt.Errorf("unsupported Git provider '%s'", config.Provider)
+	}
+	return client, err
+}

internal/bootstrap/provider/provider.go

@@ -0,0 +1,39 @@
+/*
+Copyright 2021 The Flux 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 provider
+
+// GitProvider holds a Git provider definition.
+type GitProvider string
+
+const (
+	GitProviderGitHub GitProvider = "github"
+	GitProviderGitLab GitProvider = "gitlab"
+)
+
+// Config defines the configuration for connecting to a GitProvider.
+type Config struct {
+	// Provider defines the GitProvider.
+	Provider GitProvider
+
+	// Hostname is the HTTP/S hostname of the Provider,
+	// e.g. github.example.com.
+	Hostname string
+
+	// Token contains the token used to authenticate with the
+	// Provider.
+	Token string
+}