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/git/gogit/gogit.go

@@ -0,0 +1,198 @@
+/*
+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 gogit
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+
+	gogit "github.com/go-git/go-git/v5"
+	"github.com/go-git/go-git/v5/config"
+	"github.com/go-git/go-git/v5/plumbing"
+	"github.com/go-git/go-git/v5/plumbing/object"
+	"github.com/go-git/go-git/v5/plumbing/transport"
+
+	"github.com/fluxcd/flux2/internal/bootstrap/git"
+)
+
+type GoGit struct {
+	path       string
+	auth       transport.AuthMethod
+	repository *gogit.Repository
+}
+
+func New(path string, auth transport.AuthMethod) *GoGit {
+	return &GoGit{
+		path: path,
+		auth: auth,
+	}
+}
+
+func (g *GoGit) Init(url, branch string) (bool, error) {
+	if g.repository != nil {
+		return false, nil
+	}
+
+	r, err := gogit.PlainInit(g.path, false)
+	if err != nil {
+		return false, err
+	}
+	if _, err = r.CreateRemote(&config.RemoteConfig{
+		Name: gogit.DefaultRemoteName,
+		URLs: []string{url},
+	}); err != nil {
+		return false, err
+	}
+	branchRef := plumbing.NewBranchReferenceName(branch)
+	if err = r.CreateBranch(&config.Branch{
+		Name:   branch,
+		Remote: gogit.DefaultRemoteName,
+		Merge:  branchRef,
+	}); err != nil {
+		return false, err
+	}
+	// PlainInit assumes the initial branch to always be master, we can
+	// overwrite this by setting the reference of the Storer to a new
+	// symbolic reference (as there are no commits yet) that points
+	// the HEAD to our new branch.
+	if err = r.Storer.SetReference(plumbing.NewSymbolicReference(plumbing.HEAD, branchRef)); err != nil {
+		return false, err
+	}
+
+	g.repository = r
+	return true, nil
+}
+
+func (g *GoGit) Clone(ctx context.Context, url, branch string) (bool, error) {
+	branchRef := plumbing.NewBranchReferenceName(branch)
+	r, err := gogit.PlainCloneContext(ctx, g.path, false, &gogit.CloneOptions{
+		URL:           url,
+		Auth:          g.auth,
+		RemoteName:    gogit.DefaultRemoteName,
+		ReferenceName: branchRef,
+		SingleBranch:  true,
+
+		NoCheckout: false,
+		Progress:   nil,
+		Tags:       gogit.NoTags,
+	})
+	if err != nil {
+		if err == transport.ErrEmptyRemoteRepository || isRemoteBranchNotFoundErr(err, branchRef.String()) {
+			return g.Init(url, branch)
+		}
+		return false, err
+	}
+
+	g.repository = r
+	return true, nil
+}
+
+func (g *GoGit) Write(path string, reader io.Reader) error {
+	if g.repository == nil {
+		return git.ErrNoGitRepository
+	}
+
+	wt, err := g.repository.Worktree()
+	if err != nil {
+		return err
+	}
+
+	f, err := wt.Filesystem.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	_, err = io.Copy(f, reader)
+	return err
+}
+
+func (g *GoGit) Commit(message git.Commit) (string, error) {
+	if g.repository == nil {
+		return "", git.ErrNoGitRepository
+	}
+
+	wt, err := g.repository.Worktree()
+	if err != nil {
+		return "", err
+	}
+
+	status, err := wt.Status()
+	if err != nil {
+		return "", err
+	}
+	if status.IsClean() {
+		head, err := g.repository.Head()
+		if err != nil {
+			return "", err
+		}
+		return head.Hash().String(), git.ErrNoStagedFiles
+	}
+	if _, err = wt.Add("."); err != nil {
+		return "", err
+	}
+
+	commit, err := wt.Commit(message.Message, &gogit.CommitOptions{
+		Author: &object.Signature{
+			Name:  message.Name,
+			Email: message.Email,
+			When:  time.Now(),
+		},
+	})
+	if err != nil {
+		return "", err
+	}
+	return commit.String(), nil
+}
+
+func (g *GoGit) Push(ctx context.Context) error {
+	if g.repository == nil {
+		return git.ErrNoGitRepository
+	}
+
+	return g.repository.PushContext(ctx, &gogit.PushOptions{
+		RemoteName: gogit.DefaultRemoteName,
+		Auth:       g.auth,
+		Progress:   nil,
+	})
+}
+
+func (g *GoGit) Status() (bool, error) {
+	if g.repository == nil {
+		return false, git.ErrNoGitRepository
+	}
+	wt, err := g.repository.Worktree()
+	if err != nil {
+		return false, err
+	}
+	status, err := wt.Status()
+	if err != nil {
+		return false, err
+	}
+	return status.IsClean(), nil
+}
+
+func (g *GoGit) Path() string {
+	return g.path
+}
+
+func isRemoteBranchNotFoundErr(err error, ref string) bool {
+	return strings.Contains(err.Error(), fmt.Sprintf("couldn't find remote ref %q", ref))
+}