Add migration from GitBucket (#16767)

This PR adds [GitBucket](https://gitbucket.github.io/) as migration source.

Supported:
- Milestones
- Issues
- Pull Requests
- Comments
- Reviews
- Labels

There is no public usable instance so no integration tests added.

4 files changed, 195 insertions, 106 deletions

diff --git a/modules/convert/utils.go b/modules/convert/utils.go
index a0463d7b10..52fbcf547f 100644
--- a/modules/convert/utils.go
+++ b/modules/convert/utils.go
@@ -35,6 +35,8 @@ func ToGitServiceType(value string) structs.GitServiceType {
 		return structs.GogsService
 	case "onedev":
 		return structs.OneDevService
+	case "gitbucket":
+		return structs.GitBucketService
 	default:
 		return structs.PlainGitService
 	}
diff --git a/modules/migrations/gitbucket.go b/modules/migrations/gitbucket.go
new file mode 100644
index 0000000000..72090c2490
--- /dev/null
+++ b/modules/migrations/gitbucket.go
@@ -0,0 +1,72 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"context"
+	"net/url"
+	"strings"
+
+	"code.gitea.io/gitea/modules/migrations/base"
+	"code.gitea.io/gitea/modules/structs"
+)
+
+var (
+	_ base.Downloader        = &GitBucketDownloader{}
+	_ base.DownloaderFactory = &GitBucketDownloaderFactory{}
+)
+
+func init() {
+	RegisterDownloaderFactory(&GitBucketDownloaderFactory{})
+}
+
+// GitBucketDownloaderFactory defines a GitBucket downloader factory
+type GitBucketDownloaderFactory struct {
+}
+
+// New returns a Downloader related to this factory according MigrateOptions
+func (f *GitBucketDownloaderFactory) New(ctx context.Context, opts base.MigrateOptions) (base.Downloader, error) {
+	u, err := url.Parse(opts.CloneAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	baseURL := u.Scheme + "://" + u.Host
+	fields := strings.Split(u.Path, "/")
+	oldOwner := fields[1]
+	oldName := strings.TrimSuffix(fields[2], ".git")
+
+	return NewGitBucketDownloader(ctx, baseURL, opts.AuthUsername, opts.AuthPassword, opts.AuthToken, oldOwner, oldName), nil
+}
+
+// GitServiceType returns the type of git service
+func (f *GitBucketDownloaderFactory) GitServiceType() structs.GitServiceType {
+	return structs.GitBucketService
+}
+
+// GitBucketDownloader implements a Downloader interface to get repository information
+// from GitBucket via GithubDownloader
+type GitBucketDownloader struct {
+	*GithubDownloaderV3
+}
+
+// NewGitBucketDownloader creates a GitBucket downloader
+func NewGitBucketDownloader(ctx context.Context, baseURL, userName, password, token, repoOwner, repoName string) *GitBucketDownloader {
+	githubDownloader := NewGithubDownloaderV3(ctx, baseURL, userName, password, token, repoOwner, repoName)
+	githubDownloader.SkipReactions = true
+	return &GitBucketDownloader{
+		githubDownloader,
+	}
+}
+
+// SupportGetRepoComments return true if it supports get repo comments
+func (g *GitBucketDownloader) SupportGetRepoComments() bool {
+	return false
+}
+
+// GetReviews is not supported
+func (g *GitBucketDownloader) GetReviews(context base.IssueContext) ([]*base.Review, error) {
+	return nil, &base.ErrNotSupported{Entity: "Reviews"}
+}
diff --git a/modules/migrations/github.go b/modules/migrations/github.go
index 874cd05439..50cffc467a 100644
--- a/modules/migrations/github.go
+++ b/modules/migrations/github.go
@@ -68,15 +68,16 @@ func (f *GithubDownloaderV3Factory) GitServiceType() structs.GitServiceType {
 // from github via APIv3
 type GithubDownloaderV3 struct {
 	base.NullDownloader
-	ctx          context.Context
-	clients      []*github.Client
-	repoOwner    string
-	repoName     string
-	userName     string
-	password     string
-	rates        []*github.Rate
-	curClientIdx int
-	maxPerPage   int
+	ctx           context.Context
+	clients       []*github.Client
+	repoOwner     string
+	repoName      string
+	userName      string
+	password      string
+	rates         []*github.Rate
+	curClientIdx  int
+	maxPerPage    int
+	SkipReactions bool
 }
 
 // NewGithubDownloaderV3 creates a github Downloader via github v3 API
@@ -428,25 +429,27 @@ func (g *GithubDownloaderV3) GetIssues(page, perPage int) ([]*base.Issue, bool,
 
 		// get reactions
 		var reactions []*base.Reaction
-		for i := 1; ; i++ {
-			g.waitAndPickClient()
-			res, resp, err := g.getClient().Reactions.ListIssueReactions(g.ctx, g.repoOwner, g.repoName, issue.GetNumber(), &github.ListOptions{
-				Page:    i,
-				PerPage: perPage,
-			})
-			if err != nil {
-				return nil, false, err
-			}
-			g.setRate(&resp.Rate)
-			if len(res) == 0 {
-				break
-			}
-			for _, reaction := range res {
-				reactions = append(reactions, &base.Reaction{
-					UserID:   reaction.User.GetID(),
-					UserName: reaction.User.GetLogin(),
-					Content:  reaction.GetContent(),
+		if !g.SkipReactions {
+			for i := 1; ; i++ {
+				g.waitAndPickClient()
+				res, resp, err := g.getClient().Reactions.ListIssueReactions(g.ctx, g.repoOwner, g.repoName, issue.GetNumber(), &github.ListOptions{
+					Page:    i,
+					PerPage: perPage,
 				})
+				if err != nil {
+					return nil, false, err
+				}
+				g.setRate(&resp.Rate)
+				if len(res) == 0 {
+					break
+				}
+				for _, reaction := range res {
+					reactions = append(reactions, &base.Reaction{
+						UserID:   reaction.User.GetID(),
+						UserName: reaction.User.GetLogin(),
+						Content:  reaction.GetContent(),
+					})
+				}
 			}
 		}
 
@@ -516,25 +519,27 @@ func (g *GithubDownloaderV3) getComments(issueContext base.IssueContext) ([]*bas
 		for _, comment := range comments {
 			// get reactions
 			var reactions []*base.Reaction
-			for i := 1; ; i++ {
-				g.waitAndPickClient()
-				res, resp, err := g.getClient().Reactions.ListIssueCommentReactions(g.ctx, g.repoOwner, g.repoName, comment.GetID(), &github.ListOptions{
-					Page:    i,
-					PerPage: g.maxPerPage,
-				})
-				if err != nil {
-					return nil, err
-				}
-				g.setRate(&resp.Rate)
-				if len(res) == 0 {
-					break
-				}
-				for _, reaction := range res {
-					reactions = append(reactions, &base.Reaction{
-						UserID:   reaction.User.GetID(),
-						UserName: reaction.User.GetLogin(),
-						Content:  reaction.GetContent(),
+			if !g.SkipReactions {
+				for i := 1; ; i++ {
+					g.waitAndPickClient()
+					res, resp, err := g.getClient().Reactions.ListIssueCommentReactions(g.ctx, g.repoOwner, g.repoName, comment.GetID(), &github.ListOptions{
+						Page:    i,
+						PerPage: g.maxPerPage,
 					})
+					if err != nil {
+						return nil, err
+					}
+					g.setRate(&resp.Rate)
+					if len(res) == 0 {
+						break
+					}
+					for _, reaction := range res {
+						reactions = append(reactions, &base.Reaction{
+							UserID:   reaction.User.GetID(),
+							UserName: reaction.User.GetLogin(),
+							Content:  reaction.GetContent(),
+						})
+					}
 				}
 			}
 
@@ -588,25 +593,27 @@ func (g *GithubDownloaderV3) GetAllComments(page, perPage int) ([]*base.Comment,
 	for _, comment := range comments {
 		// get reactions
 		var reactions []*base.Reaction
-		for i := 1; ; i++ {
-			g.waitAndPickClient()
-			res, resp, err := g.getClient().Reactions.ListIssueCommentReactions(g.ctx, g.repoOwner, g.repoName, comment.GetID(), &github.ListOptions{
-				Page:    i,
-				PerPage: g.maxPerPage,
-			})
-			if err != nil {
-				return nil, false, err
-			}
-			g.setRate(&resp.Rate)
-			if len(res) == 0 {
-				break
-			}
-			for _, reaction := range res {
-				reactions = append(reactions, &base.Reaction{
-					UserID:   reaction.User.GetID(),
-					UserName: reaction.User.GetLogin(),
-					Content:  reaction.GetContent(),
+		if !g.SkipReactions {
+			for i := 1; ; i++ {
+				g.waitAndPickClient()
+				res, resp, err := g.getClient().Reactions.ListIssueCommentReactions(g.ctx, g.repoOwner, g.repoName, comment.GetID(), &github.ListOptions{
+					Page:    i,
+					PerPage: g.maxPerPage,
 				})
+				if err != nil {
+					return nil, false, err
+				}
+				g.setRate(&resp.Rate)
+				if len(res) == 0 {
+					break
+				}
+				for _, reaction := range res {
+					reactions = append(reactions, &base.Reaction{
+						UserID:   reaction.User.GetID(),
+						UserName: reaction.User.GetLogin(),
+						Content:  reaction.GetContent(),
+					})
+				}
 			}
 		}
 		idx := strings.LastIndex(*comment.IssueURL, "/")
@@ -656,25 +663,27 @@ func (g *GithubDownloaderV3) GetPullRequests(page, perPage int) ([]*base.PullReq
 
 		// get reactions
 		var reactions []*base.Reaction
-		for i := 1; ; i++ {
-			g.waitAndPickClient()
-			res, resp, err := g.getClient().Reactions.ListIssueReactions(g.ctx, g.repoOwner, g.repoName, pr.GetNumber(), &github.ListOptions{
-				Page:    i,
-				PerPage: perPage,
-			})
-			if err != nil {
-				return nil, false, err
-			}
-			g.setRate(&resp.Rate)
-			if len(res) == 0 {
-				break
-			}
-			for _, reaction := range res {
-				reactions = append(reactions, &base.Reaction{
-					UserID:   reaction.User.GetID(),
-					UserName: reaction.User.GetLogin(),
-					Content:  reaction.GetContent(),
+		if !g.SkipReactions {
+			for i := 1; ; i++ {
+				g.waitAndPickClient()
+				res, resp, err := g.getClient().Reactions.ListIssueReactions(g.ctx, g.repoOwner, g.repoName, pr.GetNumber(), &github.ListOptions{
+					Page:    i,
+					PerPage: perPage,
 				})
+				if err != nil {
+					return nil, false, err
+				}
+				g.setRate(&resp.Rate)
+				if len(res) == 0 {
+					break
+				}
+				for _, reaction := range res {
+					reactions = append(reactions, &base.Reaction{
+						UserID:   reaction.User.GetID(),
+						UserName: reaction.User.GetLogin(),
+						Content:  reaction.GetContent(),
+					})
+				}
 			}
 		}
 
@@ -737,25 +746,27 @@ func (g *GithubDownloaderV3) convertGithubReviewComments(cs []*github.PullReques
 	for _, c := range cs {
 		// get reactions
 		var reactions []*base.Reaction
-		for i := 1; ; i++ {
-			g.waitAndPickClient()
-			res, resp, err := g.getClient().Reactions.ListPullRequestCommentReactions(g.ctx, g.repoOwner, g.repoName, c.GetID(), &github.ListOptions{
-				Page:    i,
-				PerPage: g.maxPerPage,
-			})
-			if err != nil {
-				return nil, err
-			}
-			g.setRate(&resp.Rate)
-			if len(res) == 0 {
-				break
-			}
-			for _, reaction := range res {
-				reactions = append(reactions, &base.Reaction{
-					UserID:   reaction.User.GetID(),
-					UserName: reaction.User.GetLogin(),
-					Content:  reaction.GetContent(),
+		if !g.SkipReactions {
+			for i := 1; ; i++ {
+				g.waitAndPickClient()
+				res, resp, err := g.getClient().Reactions.ListPullRequestCommentReactions(g.ctx, g.repoOwner, g.repoName, c.GetID(), &github.ListOptions{
+					Page:    i,
+					PerPage: g.maxPerPage,
 				})
+				if err != nil {
+					return nil, err
+				}
+				g.setRate(&resp.Rate)
+				if len(res) == 0 {
+					break
+				}
+				for _, reaction := range res {
+					reactions = append(reactions, &base.Reaction{
+						UserID:   reaction.User.GetID(),
+						UserName: reaction.User.GetLogin(),
+						Content:  reaction.GetContent(),
+					})
+				}
 			}
 		}
 
diff --git a/modules/structs/repo.go b/modules/structs/repo.go
index 313a982f43..8482a2128d 100644
--- a/modules/structs/repo.go
+++ b/modules/structs/repo.go
@@ -242,13 +242,14 @@ type GitServiceType int
 
 // enumerate all GitServiceType
 const (
-	NotMigrated     GitServiceType = iota // 0 not migrated from external sites
-	PlainGitService                       // 1 plain git service
-	GithubService                         // 2 github.com
-	GiteaService                          // 3 gitea service
-	GitlabService                         // 4 gitlab service
-	GogsService                           // 5 gogs service
-	OneDevService                         // 6 onedev service
+	NotMigrated      GitServiceType = iota // 0 not migrated from external sites
+	PlainGitService                        // 1 plain git service
+	GithubService                          // 2 github.com
+	GiteaService                           // 3 gitea service
+	GitlabService                          // 4 gitlab service
+	GogsService                            // 5 gogs service
+	OneDevService                          // 6 onedev service
+	GitBucketService                       // 7 gitbucket service
 )
 
 // Name represents the service type's name
@@ -270,6 +271,8 @@ func (gt GitServiceType) Title() string {
 		return "Gogs"
 	case OneDevService:
 		return "OneDev"
+	case GitBucketService:
+		return "GitBucket"
 	case PlainGitService:
 		return "Git"
 	}
@@ -326,5 +329,6 @@ var (
 		GiteaService,
 		GogsService,
 		OneDevService,
+		GitBucketService,
 	}
 )