Store the foreign ID of issues during migration (#18446)

Storing the foreign identifier of an imported issue in the database is a prerequisite to implement idempotent migrations or mirror for issues. It is a baby step towards mirroring that introduces a new table.

At the moment when an issue is created by the Gitea uploader, it fails if the issue already exists. The Gitea uploader could be modified so that, instead of failing, it looks up the database to find an existing issue. And if it does it would update the issue instead of creating a new one. However this is not currently possible because an information is missing from the database: the foreign identifier that uniquely represents the issue being migrated is not persisted. With this change, the foreign identifier is stored in the database and the Gitea uploader will then be able to run a query to figure out if a given issue being imported already exists.

The implementation of mirroring for issues, pull requests, releases, etc. can be done in three steps:

1. Store an identifier for the element being mirrored (issue, pull request...) in the database (this is the purpose of these changes)
2. Modify the Gitea uploader to be able to update an existing repository with all it contains (issues, pull request...) instead of failing if it exists
3. Optimize the Gitea uploader to speed up the updates, when possible.

The second step creates code that does not yet exist to enable idempotent migrations with the Gitea uploader. When a migration is done for the first time, the behavior is not changed. But when a migration is done for a repository that already exists, this new code is used to update it.

The third step can use the code created in the second step to optimize and speed up migrations. For instance, when a migration is resumed, an issue that has an update time that is not more recent can be skipped and only newly created issues or updated ones will be updated. Another example of optimization could be that a webhook notifies Gitea when an issue is updated. The code triggered by the webhook would download only this issue and call the code created in the second step to update the issue, as if it was in the process of an idempotent migration.

The ForeignReferences table is added to contain local and foreign ID pairs relative to a given repository. It can later be used for pull requests and other artifacts that can be mirrored. Although the foreign id could be added as a single field in issues or pull requests, it would need to be added to all tables that represent something that can be mirrored. Creating a new table makes for a simpler and more generic design. The drawback is that it requires an extra lookup to obtain the information. However, this extra information is only required during migration or mirroring and does not impact the way Gitea currently works.

The foreign identifier of an issue or pull request is similar to the identifier of an external user, which is stored in reactions, issues, etc. as OriginalPosterID and so on. The representation of a user is however different and the ability of users to link their account to an external user at a later time is also a logic that is different from what is involved in mirroring or migrations. For these reasons, despite some commonalities, it is unclear at this time how the two tables (foreign reference and external user) could be merged together.

The ForeignID field is extracted from the issue migration context so that it can be dumped in files with dump-repo and later restored via restore-repo.

The GetAllComments downloader method is introduced to simplify the implementation and not overload the Context for the purpose of pagination. It also clarifies in which context the comments are paginated and in which context they are not.

The Context interface is no longer useful for the purpose of retrieving the LocalID and ForeignID since they are now both available from the PullRequest and Issue struct. The Reviewable and Commentable interfaces replace and serve the same purpose.

The Context data member of PullRequest and Issue becomes a DownloaderContext to clarify that its purpose is not to support in memory operations while the current downloader is acting but is not otherwise persisted. It is, for instance, used by the GitLab downloader to store the IsMergeRequest boolean and sort out issues.

---
[source](https://lab.forgefriends.org/forgefriends/forgefriends/-/merge_requests/36)

Signed-off-by: Loïc Dachary <loic@dachary.org>
Co-authored-by: Loïc Dachary <loic@dachary.org>

16 files changed, 181 insertions, 274 deletions

diff --git a/services/migrations/codebase.go b/services/migrations/codebase.go
index be0b5d4004..bb74c0a49d 100644
--- a/services/migrations/codebase.go
+++ b/services/migrations/codebase.go
@@ -266,17 +266,7 @@ func (d *CodebaseDownloader) GetLabels() ([]*base.Label, error) {
 }
 
 type codebaseIssueContext struct {
-	foreignID int64
-	localID   int64
-	Comments  []*base.Comment
-}
-
-func (c codebaseIssueContext) LocalID() int64 {
-	return c.localID
-}
-
-func (c codebaseIssueContext) ForeignID() int64 {
-	return c.foreignID
+	Comments []*base.Comment
 }
 
 // GetIssues returns issues, limits are not supported
@@ -402,10 +392,9 @@ func (d *CodebaseDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool,
 			Labels: []*base.Label{
 				{Name: issue.Type.Name},
 			},
+			ForeignIndex: issue.TicketID.Value,
 			Context: codebaseIssueContext{
-				foreignID: issue.TicketID.Value,
-				localID:   issue.TicketID.Value,
-				Comments:  comments[1:],
+				Comments: comments[1:],
 			},
 		})
 
@@ -418,10 +407,10 @@ func (d *CodebaseDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool,
 }
 
 // GetComments returns comments
-func (d *CodebaseDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Comment, bool, error) {
-	context, ok := opts.Context.(codebaseIssueContext)
+func (d *CodebaseDownloader) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
+	context, ok := commentable.GetContext().(codebaseIssueContext)
 	if !ok {
-		return nil, false, fmt.Errorf("unexpected comment context: %+v", opts.Context)
+		return nil, false, fmt.Errorf("unexpected context: %+v", commentable.GetContext())
 	}
 
 	return context.Comments, true, nil
@@ -570,10 +559,9 @@ func (d *CodebaseDownloader) GetPullRequests(page, perPage int) ([]*base.PullReq
 				SHA:      d.getHeadCommit(rawMergeRequest.TargetRef),
 				RepoName: d.repoName,
 			},
+			ForeignIndex: rawMergeRequest.ID.Value,
 			Context: codebaseIssueContext{
-				foreignID: rawMergeRequest.ID.Value,
-				localID:   number,
-				Comments:  comments[1:],
+				Comments: comments[1:],
 			},
 		})
 	}
@@ -581,16 +569,6 @@ func (d *CodebaseDownloader) GetPullRequests(page, perPage int) ([]*base.PullReq
 	return pullRequests, true, nil
 }
 
-// GetReviews returns pull requests reviews
-func (d *CodebaseDownloader) GetReviews(context base.IssueContext) ([]*base.Review, error) {
-	return []*base.Review{}, nil
-}
-
-// GetTopics return repository topics
-func (d *CodebaseDownloader) GetTopics() ([]string, error) {
-	return []string{}, nil
-}
-
 func (d *CodebaseDownloader) tryGetUser(userID int64) *codebaseUser {
 	if len(d.userMap) == 0 {
 		var rawUsers struct {
diff --git a/services/migrations/codebase_test.go b/services/migrations/codebase_test.go
index ef39b9f146..cb70a2bf75 100644
--- a/services/migrations/codebase_test.go
+++ b/services/migrations/codebase_test.go
@@ -108,9 +108,7 @@ func TestCodebaseDownloadRepo(t *testing.T) {
 		},
 	}, issues)
 
-	comments, _, err := downloader.GetComments(base.GetCommentOptions{
-		Context: issues[0].Context,
-	})
+	comments, _, err := downloader.GetComments(issues[0])
 	assert.NoError(t, err)
 	assertCommentsEqual(t, []*base.Comment{
 		{
@@ -148,7 +146,7 @@ func TestCodebaseDownloadRepo(t *testing.T) {
 		},
 	}, prs)
 
-	rvs, err := downloader.GetReviews(prs[0].Context)
+	rvs, err := downloader.GetReviews(prs[0])
 	assert.NoError(t, err)
 	assert.Empty(t, rvs)
 }
diff --git a/services/migrations/gitbucket.go b/services/migrations/gitbucket.go
index c4fb0df93a..92b6cac738 100644
--- a/services/migrations/gitbucket.go
+++ b/services/migrations/gitbucket.go
@@ -64,8 +64,3 @@ func NewGitBucketDownloader(ctx context.Context, baseURL, userName, password, to
 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/services/migrations/gitea_downloader.go b/services/migrations/gitea_downloader.go
index be3c6c1202..3c02e112ca 100644
--- a/services/migrations/gitea_downloader.go
+++ b/services/migrations/gitea_downloader.go
@@ -415,22 +415,22 @@ func (g *GiteaDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, err
 		}
 
 		allIssues = append(allIssues, &base.Issue{
-			Title:       issue.Title,
-			Number:      issue.Index,
-			PosterID:    issue.Poster.ID,
-			PosterName:  issue.Poster.UserName,
-			PosterEmail: issue.Poster.Email,
-			Content:     issue.Body,
-			Milestone:   milestone,
-			State:       string(issue.State),
-			Created:     issue.Created,
-			Updated:     issue.Updated,
-			Closed:      issue.Closed,
-			Reactions:   reactions,
-			Labels:      labels,
-			Assignees:   assignees,
-			IsLocked:    issue.IsLocked,
-			Context:     base.BasicIssueContext(issue.Index),
+			Title:        issue.Title,
+			Number:       issue.Index,
+			PosterID:     issue.Poster.ID,
+			PosterName:   issue.Poster.UserName,
+			PosterEmail:  issue.Poster.Email,
+			Content:      issue.Body,
+			Milestone:    milestone,
+			State:        string(issue.State),
+			Created:      issue.Created,
+			Updated:      issue.Updated,
+			Closed:       issue.Closed,
+			Reactions:    reactions,
+			Labels:       labels,
+			Assignees:    assignees,
+			IsLocked:     issue.IsLocked,
+			ForeignIndex: issue.Index,
 		})
 	}
 
@@ -442,7 +442,7 @@ func (g *GiteaDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, err
 }
 
 // GetComments returns comments according issueNumber
-func (g *GiteaDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Comment, bool, error) {
+func (g *GiteaDownloader) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
 	allComments := make([]*base.Comment, 0, g.maxPerPage)
 
 	for i := 1; ; i++ {
@@ -453,26 +453,26 @@ func (g *GiteaDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Comm
 		default:
 		}
 
-		comments, _, err := g.client.ListIssueComments(g.repoOwner, g.repoName, opts.Context.ForeignID(), gitea_sdk.ListIssueCommentOptions{ListOptions: gitea_sdk.ListOptions{
+		comments, _, err := g.client.ListIssueComments(g.repoOwner, g.repoName, commentable.GetForeignIndex(), gitea_sdk.ListIssueCommentOptions{ListOptions: gitea_sdk.ListOptions{
 			PageSize: g.maxPerPage,
 			Page:     i,
 		}})
 		if err != nil {
-			return nil, false, fmt.Errorf("error while listing comments for issue #%d. Error: %v", opts.Context.ForeignID(), err)
+			return nil, false, fmt.Errorf("error while listing comments for issue #%d. Error: %v", commentable.GetForeignIndex(), err)
 		}
 
 		for _, comment := range comments {
 			reactions, err := g.getCommentReactions(comment.ID)
 			if err != nil {
-				log.Warn("Unable to load comment reactions during migrating issue #%d for comment %d to %s/%s. Error: %v", opts.Context.ForeignID(), comment.ID, g.repoOwner, g.repoName, err)
+				log.Warn("Unable to load comment reactions during migrating issue #%d for comment %d to %s/%s. Error: %v", commentable.GetForeignIndex(), comment.ID, g.repoOwner, g.repoName, err)
 				if err2 := admin_model.CreateRepositoryNotice(
-					fmt.Sprintf("Unable to load reactions during migrating issue #%d for comment %d to %s/%s. Error: %v", opts.Context.ForeignID(), comment.ID, g.repoOwner, g.repoName, err)); err2 != nil {
+					fmt.Sprintf("Unable to load reactions during migrating issue #%d for comment %d to %s/%s. Error: %v", commentable.GetForeignIndex(), comment.ID, g.repoOwner, g.repoName, err)); err2 != nil {
 					log.Error("create repository notice failed: ", err2)
 				}
 			}
 
 			allComments = append(allComments, &base.Comment{
-				IssueIndex:  opts.Context.LocalID(),
+				IssueIndex:  commentable.GetLocalIndex(),
 				Index:       comment.ID,
 				PosterID:    comment.Poster.ID,
 				PosterName:  comment.Poster.UserName,
@@ -602,7 +602,7 @@ func (g *GiteaDownloader) GetPullRequests(page, perPage int) ([]*base.PullReques
 				RepoName:  g.repoName,
 				OwnerName: g.repoOwner,
 			},
-			Context: base.BasicIssueContext(pr.Index),
+			ForeignIndex: pr.Index,
 		})
 	}
 
@@ -614,7 +614,7 @@ func (g *GiteaDownloader) GetPullRequests(page, perPage int) ([]*base.PullReques
 }
 
 // GetReviews returns pull requests review
-func (g *GiteaDownloader) GetReviews(context base.IssueContext) ([]*base.Review, error) {
+func (g *GiteaDownloader) GetReviews(reviewable base.Reviewable) ([]*base.Review, error) {
 	if err := g.client.CheckServerVersionConstraint(">=1.12"); err != nil {
 		log.Info("GiteaDownloader: instance to old, skip GetReviews")
 		return nil, nil
@@ -630,7 +630,7 @@ func (g *GiteaDownloader) GetReviews(context base.IssueContext) ([]*base.Review,
 		default:
 		}
 
-		prl, _, err := g.client.ListPullReviews(g.repoOwner, g.repoName, context.ForeignID(), gitea_sdk.ListPullReviewsOptions{ListOptions: gitea_sdk.ListOptions{
+		prl, _, err := g.client.ListPullReviews(g.repoOwner, g.repoName, reviewable.GetForeignIndex(), gitea_sdk.ListPullReviewsOptions{ListOptions: gitea_sdk.ListOptions{
 			Page:     i,
 			PageSize: g.maxPerPage,
 		}})
@@ -640,7 +640,7 @@ func (g *GiteaDownloader) GetReviews(context base.IssueContext) ([]*base.Review,
 
 		for _, pr := range prl {
 
-			rcl, _, err := g.client.ListPullReviewComments(g.repoOwner, g.repoName, context.ForeignID(), pr.ID)
+			rcl, _, err := g.client.ListPullReviewComments(g.repoOwner, g.repoName, reviewable.GetForeignIndex(), pr.ID)
 			if err != nil {
 				return nil, err
 			}
@@ -666,7 +666,7 @@ func (g *GiteaDownloader) GetReviews(context base.IssueContext) ([]*base.Review,
 
 			allReviews = append(allReviews, &base.Review{
 				ID:           pr.ID,
-				IssueIndex:   context.LocalID(),
+				IssueIndex:   reviewable.GetLocalIndex(),
 				ReviewerID:   pr.Reviewer.ID,
 				ReviewerName: pr.Reviewer.UserName,
 				Official:     pr.Official,
diff --git a/services/migrations/gitea_downloader_test.go b/services/migrations/gitea_downloader_test.go
index 2c70dc4213..dc6903e854 100644
--- a/services/migrations/gitea_downloader_test.go
+++ b/services/migrations/gitea_downloader_test.go
@@ -198,9 +198,7 @@ func TestGiteaDownloadRepo(t *testing.T) {
 		},
 	}, issues)
 
-	comments, _, err := downloader.GetComments(base.GetCommentOptions{
-		Context: base.BasicIssueContext(4),
-	})
+	comments, _, err := downloader.GetComments(&base.Issue{Number: 4, ForeignIndex: 4})
 	assert.NoError(t, err)
 	assertCommentsEqual(t, []*base.Comment{
 		{
@@ -265,7 +263,7 @@ func TestGiteaDownloadRepo(t *testing.T) {
 		PatchURL:       "https://gitea.com/gitea/test_repo/pulls/12.patch",
 	}, prs[1])
 
-	reviews, err := downloader.GetReviews(base.BasicIssueContext(7))
+	reviews, err := downloader.GetReviews(&base.Issue{Number: 7, ForeignIndex: 7})
 	assert.NoError(t, err)
 	assertReviewsEqual(t, []*base.Review{
 		{
diff --git a/services/migrations/gitea_uploader.go b/services/migrations/gitea_uploader.go
index 21c2dc8f8e..2faa0a1f2a 100644
--- a/services/migrations/gitea_uploader.go
+++ b/services/migrations/gitea_uploader.go
@@ -11,11 +11,13 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"time"
 
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/foreignreference"
 	repo_model "code.gitea.io/gitea/models/repo"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/git"
@@ -373,6 +375,12 @@ func (g *GiteaLocalUploader) CreateIssues(issues ...*base.Issue) error {
 			Labels:      labels,
 			CreatedUnix: timeutil.TimeStamp(issue.Created.Unix()),
 			UpdatedUnix: timeutil.TimeStamp(issue.Updated.Unix()),
+			ForeignReference: &foreignreference.ForeignReference{
+				LocalIndex:   issue.GetLocalIndex(),
+				ForeignIndex: strconv.FormatInt(issue.GetForeignIndex(), 10),
+				RepoID:       g.repo.ID,
+				Type:         foreignreference.TypeIssue,
+			},
 		}
 
 		if err := g.remapUser(issue, &is); err != nil {
diff --git a/services/migrations/github.go b/services/migrations/github.go
index f86ba94393..faf0cf0794 100644
--- a/services/migrations/github.go
+++ b/services/migrations/github.go
@@ -446,22 +446,22 @@ func (g *GithubDownloaderV3) GetIssues(page, perPage int) ([]*base.Issue, bool,
 		}
 
 		allIssues = append(allIssues, &base.Issue{
-			Title:       *issue.Title,
-			Number:      int64(*issue.Number),
-			PosterID:    issue.GetUser().GetID(),
-			PosterName:  issue.GetUser().GetLogin(),
-			PosterEmail: issue.GetUser().GetEmail(),
-			Content:     issue.GetBody(),
-			Milestone:   issue.GetMilestone().GetTitle(),
-			State:       issue.GetState(),
-			Created:     issue.GetCreatedAt(),
-			Updated:     issue.GetUpdatedAt(),
-			Labels:      labels,
-			Reactions:   reactions,
-			Closed:      issue.ClosedAt,
-			IsLocked:    issue.GetLocked(),
-			Assignees:   assignees,
-			Context:     base.BasicIssueContext(*issue.Number),
+			Title:        *issue.Title,
+			Number:       int64(*issue.Number),
+			PosterID:     issue.GetUser().GetID(),
+			PosterName:   issue.GetUser().GetLogin(),
+			PosterEmail:  issue.GetUser().GetEmail(),
+			Content:      issue.GetBody(),
+			Milestone:    issue.GetMilestone().GetTitle(),
+			State:        issue.GetState(),
+			Created:      issue.GetCreatedAt(),
+			Updated:      issue.GetUpdatedAt(),
+			Labels:       labels,
+			Reactions:    reactions,
+			Closed:       issue.ClosedAt,
+			IsLocked:     issue.GetLocked(),
+			Assignees:    assignees,
+			ForeignIndex: int64(*issue.Number),
 		})
 	}
 
@@ -474,16 +474,12 @@ func (g *GithubDownloaderV3) SupportGetRepoComments() bool {
 }
 
 // GetComments returns comments according issueNumber
-func (g *GithubDownloaderV3) GetComments(opts base.GetCommentOptions) ([]*base.Comment, bool, error) {
-	if opts.Context != nil {
-		comments, err := g.getComments(opts.Context)
-		return comments, false, err
-	}
-
-	return g.GetAllComments(opts.Page, opts.PageSize)
+func (g *GithubDownloaderV3) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
+	comments, err := g.getComments(commentable)
+	return comments, false, err
 }
 
-func (g *GithubDownloaderV3) getComments(issueContext base.IssueContext) ([]*base.Comment, error) {
+func (g *GithubDownloaderV3) getComments(commentable base.Commentable) ([]*base.Comment, error) {
 	var (
 		allComments = make([]*base.Comment, 0, g.maxPerPage)
 		created     = "created"
@@ -498,7 +494,7 @@ func (g *GithubDownloaderV3) getComments(issueContext base.IssueContext) ([]*bas
 	}
 	for {
 		g.waitAndPickClient()
-		comments, resp, err := g.getClient().Issues.ListComments(g.ctx, g.repoOwner, g.repoName, int(issueContext.ForeignID()), opt)
+		comments, resp, err := g.getClient().Issues.ListComments(g.ctx, g.repoOwner, g.repoName, int(commentable.GetForeignIndex()), opt)
 		if err != nil {
 			return nil, fmt.Errorf("error while listing repos: %v", err)
 		}
@@ -531,7 +527,7 @@ func (g *GithubDownloaderV3) getComments(issueContext base.IssueContext) ([]*bas
 			}
 
 			allComments = append(allComments, &base.Comment{
-				IssueIndex:  issueContext.LocalID(),
+				IssueIndex:  commentable.GetLocalIndex(),
 				Index:       comment.GetID(),
 				PosterID:    comment.GetUser().GetID(),
 				PosterName:  comment.GetUser().GetLogin(),
@@ -709,9 +705,9 @@ func (g *GithubDownloaderV3) GetPullRequests(page, perPage int) ([]*base.PullReq
 				RepoName:  pr.GetBase().GetRepo().GetName(),
 				OwnerName: pr.GetBase().GetUser().GetLogin(),
 			},
-			PatchURL:  pr.GetPatchURL(),
-			Reactions: reactions,
-			Context:   base.BasicIssueContext(*pr.Number),
+			PatchURL:     pr.GetPatchURL(),
+			Reactions:    reactions,
+			ForeignIndex: int64(*pr.Number),
 		})
 	}
 
@@ -777,28 +773,28 @@ func (g *GithubDownloaderV3) convertGithubReviewComments(cs []*github.PullReques
 }
 
 // GetReviews returns pull requests review
-func (g *GithubDownloaderV3) GetReviews(context base.IssueContext) ([]*base.Review, error) {
+func (g *GithubDownloaderV3) GetReviews(reviewable base.Reviewable) ([]*base.Review, error) {
 	allReviews := make([]*base.Review, 0, g.maxPerPage)
 	opt := &github.ListOptions{
 		PerPage: g.maxPerPage,
 	}
 	for {
 		g.waitAndPickClient()
-		reviews, resp, err := g.getClient().PullRequests.ListReviews(g.ctx, g.repoOwner, g.repoName, int(context.ForeignID()), opt)
+		reviews, resp, err := g.getClient().PullRequests.ListReviews(g.ctx, g.repoOwner, g.repoName, int(reviewable.GetForeignIndex()), opt)
 		if err != nil {
 			return nil, fmt.Errorf("error while listing repos: %v", err)
 		}
 		g.setRate(&resp.Rate)
 		for _, review := range reviews {
 			r := convertGithubReview(review)
-			r.IssueIndex = context.LocalID()
+			r.IssueIndex = reviewable.GetLocalIndex()
 			// retrieve all review comments
 			opt2 := &github.ListOptions{
 				PerPage: g.maxPerPage,
 			}
 			for {
 				g.waitAndPickClient()
-				reviewComments, resp, err := g.getClient().PullRequests.ListReviewComments(g.ctx, g.repoOwner, g.repoName, int(context.ForeignID()), review.GetID(), opt2)
+				reviewComments, resp, err := g.getClient().PullRequests.ListReviewComments(g.ctx, g.repoOwner, g.repoName, int(reviewable.GetForeignIndex()), review.GetID(), opt2)
 				if err != nil {
 					return nil, fmt.Errorf("error while listing repos: %v", err)
 				}
diff --git a/services/migrations/github_test.go b/services/migrations/github_test.go
index 7540037d92..90c1fcaef5 100644
--- a/services/migrations/github_test.go
+++ b/services/migrations/github_test.go
@@ -215,9 +215,7 @@ func TestGitHubDownloadRepo(t *testing.T) {
 	}, issues)
 
 	// downloader.GetComments()
-	comments, _, err := downloader.GetComments(base.GetCommentOptions{
-		Context: base.BasicIssueContext(2),
-	})
+	comments, _, err := downloader.GetComments(&base.Issue{Number: 2, ForeignIndex: 2})
 	assert.NoError(t, err)
 	assertCommentsEqual(t, []*base.Comment{
 		{
@@ -286,7 +284,7 @@ func TestGitHubDownloadRepo(t *testing.T) {
 			Merged:         true,
 			MergedTime:     timePtr(time.Date(2019, 11, 12, 21, 39, 27, 0, time.UTC)),
 			MergeCommitSHA: "f32b0a9dfd09a60f616f29158f772cedd89942d2",
-			Context:        base.BasicIssueContext(3),
+			ForeignIndex:   3,
 		},
 		{
 			Number:     4,
@@ -333,11 +331,11 @@ func TestGitHubDownloadRepo(t *testing.T) {
 					Content:  "+1",
 				},
 			},
-			Context: base.BasicIssueContext(4),
+			ForeignIndex: 4,
 		},
 	}, prs)
 
-	reviews, err := downloader.GetReviews(base.BasicIssueContext(3))
+	reviews, err := downloader.GetReviews(&base.PullRequest{Number: 3, ForeignIndex: 3})
 	assert.NoError(t, err)
 	assertReviewsEqual(t, []*base.Review{
 		{
@@ -369,7 +367,7 @@ func TestGitHubDownloadRepo(t *testing.T) {
 		},
 	}, reviews)
 
-	reviews, err = downloader.GetReviews(base.BasicIssueContext(4))
+	reviews, err = downloader.GetReviews(&base.PullRequest{Number: 4, ForeignIndex: 4})
 	assert.NoError(t, err)
 	assertReviewsEqual(t, []*base.Review{
 		{
diff --git a/services/migrations/gitlab.go b/services/migrations/gitlab.go
index c05d081e9a..d3a034e27c 100644
--- a/services/migrations/gitlab.go
+++ b/services/migrations/gitlab.go
@@ -349,19 +349,9 @@ func (g *GitlabDownloader) GetReleases() ([]*base.Release, error) {
 }
 
 type gitlabIssueContext struct {
-	foreignID      int64
-	localID        int64
 	IsMergeRequest bool
 }
 
-func (c gitlabIssueContext) LocalID() int64 {
-	return c.localID
-}
-
-func (c gitlabIssueContext) ForeignID() int64 {
-	return c.foreignID
-}
-
 // GetIssues returns issues according start and limit
 //   Note: issue label description and colors are not supported by the go-gitlab library at this time
 func (g *GitlabDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, error) {
@@ -421,24 +411,21 @@ func (g *GitlabDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, er
 		}
 
 		allIssues = append(allIssues, &base.Issue{
-			Title:      issue.Title,
-			Number:     int64(issue.IID),
-			PosterID:   int64(issue.Author.ID),
-			PosterName: issue.Author.Username,
-			Content:    issue.Description,
-			Milestone:  milestone,
-			State:      issue.State,
-			Created:    *issue.CreatedAt,
-			Labels:     labels,
-			Reactions:  reactions,
-			Closed:     issue.ClosedAt,
-			IsLocked:   issue.DiscussionLocked,
-			Updated:    *issue.UpdatedAt,
-			Context: gitlabIssueContext{
-				foreignID:      int64(issue.IID),
-				localID:        int64(issue.IID),
-				IsMergeRequest: false,
-			},
+			Title:        issue.Title,
+			Number:       int64(issue.IID),
+			PosterID:     int64(issue.Author.ID),
+			PosterName:   issue.Author.Username,
+			Content:      issue.Description,
+			Milestone:    milestone,
+			State:        issue.State,
+			Created:      *issue.CreatedAt,
+			Labels:       labels,
+			Reactions:    reactions,
+			Closed:       issue.ClosedAt,
+			IsLocked:     issue.DiscussionLocked,
+			Updated:      *issue.UpdatedAt,
+			ForeignIndex: int64(issue.IID),
+			Context:      gitlabIssueContext{IsMergeRequest: false},
 		})
 
 		// increment issueCount, to be used in GetPullRequests()
@@ -450,10 +437,10 @@ func (g *GitlabDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, er
 
 // GetComments returns comments according issueNumber
 // TODO: figure out how to transfer comment reactions
-func (g *GitlabDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Comment, bool, error) {
-	context, ok := opts.Context.(gitlabIssueContext)
+func (g *GitlabDownloader) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
+	context, ok := commentable.GetContext().(gitlabIssueContext)
 	if !ok {
-		return nil, false, fmt.Errorf("unexpected context: %+v", opts.Context)
+		return nil, false, fmt.Errorf("unexpected context: %+v", commentable.GetContext())
 	}
 
 	allComments := make([]*base.Comment, 0, g.maxPerPage)
@@ -465,12 +452,12 @@ func (g *GitlabDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Com
 		var resp *gitlab.Response
 		var err error
 		if !context.IsMergeRequest {
-			comments, resp, err = g.client.Discussions.ListIssueDiscussions(g.repoID, int(context.ForeignID()), &gitlab.ListIssueDiscussionsOptions{
+			comments, resp, err = g.client.Discussions.ListIssueDiscussions(g.repoID, int(commentable.GetForeignIndex()), &gitlab.ListIssueDiscussionsOptions{
 				Page:    page,
 				PerPage: g.maxPerPage,
 			}, nil, gitlab.WithContext(g.ctx))
 		} else {
-			comments, resp, err = g.client.Discussions.ListMergeRequestDiscussions(g.repoID, int(context.ForeignID()), &gitlab.ListMergeRequestDiscussionsOptions{
+			comments, resp, err = g.client.Discussions.ListMergeRequestDiscussions(g.repoID, int(commentable.GetForeignIndex()), &gitlab.ListMergeRequestDiscussionsOptions{
 				Page:    page,
 				PerPage: g.maxPerPage,
 			}, nil, gitlab.WithContext(g.ctx))
@@ -484,7 +471,7 @@ func (g *GitlabDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Com
 			if !comment.IndividualNote {
 				for _, note := range comment.Notes {
 					allComments = append(allComments, &base.Comment{
-						IssueIndex:  context.LocalID(),
+						IssueIndex:  commentable.GetLocalIndex(),
 						Index:       int64(note.ID),
 						PosterID:    int64(note.Author.ID),
 						PosterName:  note.Author.Username,
@@ -496,7 +483,7 @@ func (g *GitlabDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Com
 			} else {
 				c := comment.Notes[0]
 				allComments = append(allComments, &base.Comment{
-					IssueIndex:  context.LocalID(),
+					IssueIndex:  commentable.GetLocalIndex(),
 					Index:       int64(c.ID),
 					PosterID:    int64(c.Author.ID),
 					PosterName:  c.Author.Username,
@@ -619,12 +606,9 @@ func (g *GitlabDownloader) GetPullRequests(page, perPage int) ([]*base.PullReque
 				RepoName:  g.repoName,
 				OwnerName: pr.Author.Username,
 			},
-			PatchURL: pr.WebURL + ".patch",
-			Context: gitlabIssueContext{
-				foreignID:      int64(pr.IID),
-				localID:        newPRNumber,
-				IsMergeRequest: true,
-			},
+			PatchURL:     pr.WebURL + ".patch",
+			ForeignIndex: int64(pr.IID),
+			Context:      gitlabIssueContext{IsMergeRequest: true},
 		})
 	}
 
@@ -632,8 +616,8 @@ func (g *GitlabDownloader) GetPullRequests(page, perPage int) ([]*base.PullReque
 }
 
 // GetReviews returns pull requests review
-func (g *GitlabDownloader) GetReviews(context base.IssueContext) ([]*base.Review, error) {
-	approvals, resp, err := g.client.MergeRequestApprovals.GetConfiguration(g.repoID, int(context.ForeignID()), gitlab.WithContext(g.ctx))
+func (g *GitlabDownloader) GetReviews(reviewable base.Reviewable) ([]*base.Review, error) {
+	approvals, resp, err := g.client.MergeRequestApprovals.GetConfiguration(g.repoID, int(reviewable.GetForeignIndex()), gitlab.WithContext(g.ctx))
 	if err != nil {
 		if resp != nil && resp.StatusCode == 404 {
 			log.Error(fmt.Sprintf("GitlabDownloader: while migrating a error occurred: '%s'", err.Error()))
@@ -654,7 +638,7 @@ func (g *GitlabDownloader) GetReviews(context base.IssueContext) ([]*base.Review
 	reviews := make([]*base.Review, 0, len(approvals.ApprovedBy))
 	for _, user := range approvals.ApprovedBy {
 		reviews = append(reviews, &base.Review{
-			IssueIndex:   context.LocalID(),
+			IssueIndex:   reviewable.GetLocalIndex(),
 			ReviewerID:   int64(user.User.ID),
 			ReviewerName: user.User.Username,
 			CreatedAt:    createdAt,
diff --git a/services/migrations/gitlab_test.go b/services/migrations/gitlab_test.go
index ad61577653..52edb2af8f 100644
--- a/services/migrations/gitlab_test.go
+++ b/services/migrations/gitlab_test.go
@@ -214,12 +214,10 @@ func TestGitlabDownloadRepo(t *testing.T) {
 		},
 	}, issues)
 
-	comments, _, err := downloader.GetComments(base.GetCommentOptions{
-		Context: gitlabIssueContext{
-			foreignID:      2,
-			localID:        2,
-			IsMergeRequest: false,
-		},
+	comments, _, err := downloader.GetComments(&base.Issue{
+		Number:       2,
+		ForeignIndex: 2,
+		Context:      gitlabIssueContext{IsMergeRequest: false},
 	})
 	assert.NoError(t, err)
 	assertCommentsEqual(t, []*base.Comment{
@@ -301,15 +299,12 @@ func TestGitlabDownloadRepo(t *testing.T) {
 			Merged:         false,
 			MergedTime:     nil,
 			MergeCommitSHA: "",
-			Context: gitlabIssueContext{
-				foreignID:      2,
-				localID:        4,
-				IsMergeRequest: true,
-			},
+			ForeignIndex:   2,
+			Context:        gitlabIssueContext{IsMergeRequest: true},
 		},
 	}, prs)
 
-	rvs, err := downloader.GetReviews(base.BasicIssueContext(1))
+	rvs, err := downloader.GetReviews(&base.PullRequest{Number: 1, ForeignIndex: 1})
 	assert.NoError(t, err)
 	assertReviewsEqual(t, []*base.Review{
 		{
@@ -328,7 +323,7 @@ func TestGitlabDownloadRepo(t *testing.T) {
 		},
 	}, rvs)
 
-	rvs, err = downloader.GetReviews(base.BasicIssueContext(2))
+	rvs, err = downloader.GetReviews(&base.PullRequest{Number: 2, ForeignIndex: 2})
 	assert.NoError(t, err)
 	assertReviewsEqual(t, []*base.Review{
 		{
@@ -469,7 +464,8 @@ func TestGitlabGetReviews(t *testing.T) {
 		mock, review := convertTestCase(testCase)
 		mux.HandleFunc(fmt.Sprintf("/api/v4/projects/%d/merge_requests/%d/approvals", testCase.repoID, testCase.prID), mock)
 
-		rvs, err := downloader.GetReviews(base.BasicIssueContext(testCase.prID))
+		id := int64(testCase.prID)
+		rvs, err := downloader.GetReviews(&base.Issue{Number: id, ForeignIndex: id})
 		assert.NoError(t, err)
 		assertReviewsEqual(t, []*base.Review{&review}, rvs)
 	}
diff --git a/services/migrations/gogs.go b/services/migrations/gogs.go
index 0ef39484b7..a28033218e 100644
--- a/services/migrations/gogs.go
+++ b/services/migrations/gogs.go
@@ -223,10 +223,10 @@ func (g *GogsDownloader) getIssues(page int, state string) ([]*base.Issue, bool,
 }
 
 // GetComments returns comments according issueNumber
-func (g *GogsDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Comment, bool, error) {
+func (g *GogsDownloader) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
 	allComments := make([]*base.Comment, 0, 100)
 
-	comments, err := g.client.ListIssueComments(g.repoOwner, g.repoName, opts.Context.ForeignID())
+	comments, err := g.client.ListIssueComments(g.repoOwner, g.repoName, commentable.GetForeignIndex())
 	if err != nil {
 		return nil, false, fmt.Errorf("error while listing repos: %v", err)
 	}
@@ -235,7 +235,7 @@ func (g *GogsDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Comme
 			continue
 		}
 		allComments = append(allComments, &base.Comment{
-			IssueIndex:  opts.Context.LocalID(),
+			IssueIndex:  commentable.GetLocalIndex(),
 			Index:       comment.ID,
 			PosterID:    comment.Poster.ID,
 			PosterName:  comment.Poster.Login,
@@ -288,19 +288,19 @@ func convertGogsIssue(issue *gogs.Issue) *base.Issue {
 	}
 
 	return &base.Issue{
-		Title:       issue.Title,
-		Number:      issue.Index,
-		PosterID:    issue.Poster.ID,
-		PosterName:  issue.Poster.Login,
-		PosterEmail: issue.Poster.Email,
-		Content:     issue.Body,
-		Milestone:   milestone,
-		State:       string(issue.State),
-		Created:     issue.Created,
-		Updated:     issue.Updated,
-		Labels:      labels,
-		Closed:      closed,
-		Context:     base.BasicIssueContext(issue.Index),
+		Title:        issue.Title,
+		Number:       issue.Index,
+		PosterID:     issue.Poster.ID,
+		PosterName:   issue.Poster.Login,
+		PosterEmail:  issue.Poster.Email,
+		Content:      issue.Body,
+		Milestone:    milestone,
+		State:        string(issue.State),
+		Created:      issue.Created,
+		Updated:      issue.Updated,
+		Labels:       labels,
+		Closed:       closed,
+		ForeignIndex: issue.Index,
 	}
 }
 
diff --git a/services/migrations/gogs_test.go b/services/migrations/gogs_test.go
index f9d74d3be3..501161b610 100644
--- a/services/migrations/gogs_test.go
+++ b/services/migrations/gogs_test.go
@@ -111,9 +111,7 @@ func TestGogsDownloadRepo(t *testing.T) {
 	}, issues)
 
 	// downloader.GetComments()
-	comments, _, err := downloader.GetComments(base.GetCommentOptions{
-		Context: base.BasicIssueContext(1),
-	})
+	comments, _, err := downloader.GetComments(&base.Issue{Number: 1, ForeignIndex: 1})
 	assert.NoError(t, err)
 	assertCommentsEqual(t, []*base.Comment{
 		{
diff --git a/services/migrations/migrate.go b/services/migrations/migrate.go
index 7bca128ac5..b550be4ce7 100644
--- a/services/migrations/migrate.go
+++ b/services/migrations/migrate.go
@@ -325,9 +325,7 @@ func migrateRepository(downloader base.Downloader, uploader base.Uploader, opts
 				allComments := make([]*base.Comment, 0, commentBatchSize)
 				for _, issue := range issues {
 					log.Trace("migrating issue %d's comments", issue.Number)
-					comments, _, err := downloader.GetComments(base.GetCommentOptions{
-						Context: issue.Context,
-					})
+					comments, _, err := downloader.GetComments(issue)
 					if err != nil {
 						if !base.IsErrNotSupported(err) {
 							return err
@@ -383,9 +381,7 @@ func migrateRepository(downloader base.Downloader, uploader base.Uploader, opts
 					allComments := make([]*base.Comment, 0, commentBatchSize)
 					for _, pr := range prs {
 						log.Trace("migrating pull request %d's comments", pr.Number)
-						comments, _, err := downloader.GetComments(base.GetCommentOptions{
-							Context: pr.Context,
-						})
+						comments, _, err := downloader.GetComments(pr)
 						if err != nil {
 							if !base.IsErrNotSupported(err) {
 								return err
@@ -412,7 +408,7 @@ func migrateRepository(downloader base.Downloader, uploader base.Uploader, opts
 				// migrate reviews
 				allReviews := make([]*base.Review, 0, reviewBatchSize)
 				for _, pr := range prs {
-					reviews, err := downloader.GetReviews(pr.Context)
+					reviews, err := downloader.GetReviews(pr)
 					if err != nil {
 						if !base.IsErrNotSupported(err) {
 							return err
@@ -446,10 +442,7 @@ func migrateRepository(downloader base.Downloader, uploader base.Uploader, opts
 	if opts.Comments && supportAllComments {
 		log.Trace("migrating comments")
 		for i := 1; ; i++ {
-			comments, isEnd, err := downloader.GetComments(base.GetCommentOptions{
-				Page:     i,
-				PageSize: commentBatchSize,
-			})
+			comments, isEnd, err := downloader.GetAllComments(i, commentBatchSize)
 			if err != nil {
 				return err
 			}
diff --git a/services/migrations/onedev.go b/services/migrations/onedev.go
index d27cbbed4f..d4b30939ce 100644
--- a/services/migrations/onedev.go
+++ b/services/migrations/onedev.go
@@ -262,19 +262,9 @@ func (d *OneDevDownloader) GetLabels() ([]*base.Label, error) {
 }
 
 type onedevIssueContext struct {
-	foreignID     int64
-	localID       int64
 	IsPullRequest bool
 }
 
-func (c onedevIssueContext) LocalID() int64 {
-	return c.localID
-}
-
-func (c onedevIssueContext) ForeignID() int64 {
-	return c.foreignID
-}
-
 // GetIssues returns issues
 func (d *OneDevDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, error) {
 	rawIssues := make([]struct {
@@ -346,21 +336,18 @@ func (d *OneDevDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, er
 		}
 		poster := d.tryGetUser(issue.SubmitterID)
 		issues = append(issues, &base.Issue{
-			Title:       issue.Title,
-			Number:      issue.Number,
-			PosterName:  poster.Name,
-			PosterEmail: poster.Email,
-			Content:     issue.Description,
-			Milestone:   d.milestoneMap[milestoneID],
-			State:       state,
-			Created:     issue.SubmitDate,
-			Updated:     issue.SubmitDate,
-			Labels:      []*base.Label{label},
-			Context: onedevIssueContext{
-				foreignID:     issue.ID,
-				localID:       issue.Number,
-				IsPullRequest: false,
-			},
+			Title:        issue.Title,
+			Number:       issue.Number,
+			PosterName:   poster.Name,
+			PosterEmail:  poster.Email,
+			Content:      issue.Description,
+			Milestone:    d.milestoneMap[milestoneID],
+			State:        state,
+			Created:      issue.SubmitDate,
+			Updated:      issue.SubmitDate,
+			Labels:       []*base.Label{label},
+			ForeignIndex: issue.ID,
+			Context:      onedevIssueContext{IsPullRequest: false},
 		})
 
 		if d.maxIssueIndex < issue.Number {
@@ -372,10 +359,10 @@ func (d *OneDevDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, er
 }
 
 // GetComments returns comments
-func (d *OneDevDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Comment, bool, error) {
-	context, ok := opts.Context.(onedevIssueContext)
+func (d *OneDevDownloader) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
+	context, ok := commentable.GetContext().(onedevIssueContext)
 	if !ok {
-		return nil, false, fmt.Errorf("unexpected comment context: %+v", opts.Context)
+		return nil, false, fmt.Errorf("unexpected context: %+v", commentable.GetContext())
 	}
 
 	rawComments := make([]struct {
@@ -387,9 +374,9 @@ func (d *OneDevDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Com
 
 	var endpoint string
 	if context.IsPullRequest {
-		endpoint = fmt.Sprintf("/api/pull-requests/%d/comments", context.ForeignID())
+		endpoint = fmt.Sprintf("/api/pull-requests/%d/comments", commentable.GetForeignIndex())
 	} else {
-		endpoint = fmt.Sprintf("/api/issues/%d/comments", context.ForeignID())
+		endpoint = fmt.Sprintf("/api/issues/%d/comments", commentable.GetForeignIndex())
 	}
 
 	err := d.callAPI(
@@ -408,9 +395,9 @@ func (d *OneDevDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Com
 	}, 0, 100)
 
 	if context.IsPullRequest {
-		endpoint = fmt.Sprintf("/api/pull-requests/%d/changes", context.ForeignID())
+		endpoint = fmt.Sprintf("/api/pull-requests/%d/changes", commentable.GetForeignIndex())
 	} else {
-		endpoint = fmt.Sprintf("/api/issues/%d/changes", context.ForeignID())
+		endpoint = fmt.Sprintf("/api/issues/%d/changes", commentable.GetForeignIndex())
 	}
 
 	err = d.callAPI(
@@ -429,7 +416,7 @@ func (d *OneDevDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Com
 		}
 		poster := d.tryGetUser(comment.UserID)
 		comments = append(comments, &base.Comment{
-			IssueIndex:  context.LocalID(),
+			IssueIndex:  commentable.GetLocalIndex(),
 			Index:       comment.ID,
 			PosterID:    poster.ID,
 			PosterName:  poster.Name,
@@ -454,7 +441,7 @@ func (d *OneDevDownloader) GetComments(opts base.GetCommentOptions) ([]*base.Com
 
 		poster := d.tryGetUser(change.UserID)
 		comments = append(comments, &base.Comment{
-			IssueIndex:  context.LocalID(),
+			IssueIndex:  commentable.GetLocalIndex(),
 			PosterID:    poster.ID,
 			PosterName:  poster.Name,
 			PosterEmail: poster.Email,
@@ -552,11 +539,8 @@ func (d *OneDevDownloader) GetPullRequests(page, perPage int) ([]*base.PullReque
 				SHA:      mergePreview.TargetHeadCommitHash,
 				RepoName: d.repoName,
 			},
-			Context: onedevIssueContext{
-				foreignID:     pr.ID,
-				localID:       number,
-				IsPullRequest: true,
-			},
+			ForeignIndex: pr.ID,
+			Context:      onedevIssueContext{IsPullRequest: true},
 		})
 	}
 
@@ -564,7 +548,7 @@ func (d *OneDevDownloader) GetPullRequests(page, perPage int) ([]*base.PullReque
 }
 
 // GetReviews returns pull requests reviews
-func (d *OneDevDownloader) GetReviews(context base.IssueContext) ([]*base.Review, error) {
+func (d *OneDevDownloader) GetReviews(reviewable base.Reviewable) ([]*base.Review, error) {
 	rawReviews := make([]struct {
 		ID     int64 `json:"id"`
 		UserID int64 `json:"userId"`
@@ -576,7 +560,7 @@ func (d *OneDevDownloader) GetReviews(context base.IssueContext) ([]*base.Review
 	}, 0, 100)
 
 	err := d.callAPI(
-		fmt.Sprintf("/api/pull-requests/%d/reviews", context.ForeignID()),
+		fmt.Sprintf("/api/pull-requests/%d/reviews", reviewable.GetForeignIndex()),
 		nil,
 		&rawReviews,
 	)
@@ -600,7 +584,7 @@ func (d *OneDevDownloader) GetReviews(context base.IssueContext) ([]*base.Review
 
 		poster := d.tryGetUser(review.UserID)
 		reviews = append(reviews, &base.Review{
-			IssueIndex:   context.LocalID(),
+			IssueIndex:   reviewable.GetLocalIndex(),
 			ReviewerID:   poster.ID,
 			ReviewerName: poster.Name,
 			Content:      content,
diff --git a/services/migrations/onedev_test.go b/services/migrations/onedev_test.go
index 59b7cae5fe..55ae7da1fc 100644
--- a/services/migrations/onedev_test.go
+++ b/services/migrations/onedev_test.go
@@ -74,11 +74,8 @@ func TestOneDevDownloadRepo(t *testing.T) {
 					Name: "Improvement",
 				},
 			},
-			Context: onedevIssueContext{
-				foreignID:     398,
-				localID:       4,
-				IsPullRequest: false,
-			},
+			ForeignIndex: 398,
+			Context:      onedevIssueContext{IsPullRequest: false},
 		},
 		{
 			Number:     3,
@@ -94,20 +91,15 @@ func TestOneDevDownloadRepo(t *testing.T) {
 					Name: "New Feature",
 				},
 			},
-			Context: onedevIssueContext{
-				foreignID:     397,
-				localID:       3,
-				IsPullRequest: false,
-			},
+			ForeignIndex: 397,
+			Context:      onedevIssueContext{IsPullRequest: false},
 		},
 	}, issues)
 
-	comments, _, err := downloader.GetComments(base.GetCommentOptions{
-		Context: onedevIssueContext{
-			foreignID:     398,
-			localID:       4,
-			IsPullRequest: false,
-		},
+	comments, _, err := downloader.GetComments(&base.Issue{
+		Number:       4,
+		ForeignIndex: 398,
+		Context:      onedevIssueContext{IsPullRequest: false},
 	})
 	assert.NoError(t, err)
 	assertCommentsEqual(t, []*base.Comment{
@@ -141,18 +133,12 @@ func TestOneDevDownloadRepo(t *testing.T) {
 				SHA:      "f32b0a9dfd09a60f616f29158f772cedd89942d2",
 				RepoName: "go-gitea-test_repo",
 			},
-			Context: onedevIssueContext{
-				foreignID:     186,
-				localID:       5,
-				IsPullRequest: true,
-			},
+			ForeignIndex: 186,
+			Context:      onedevIssueContext{IsPullRequest: true},
 		},
 	}, prs)
 
-	rvs, err := downloader.GetReviews(onedevIssueContext{
-		foreignID: 186,
-		localID:   5,
-	})
+	rvs, err := downloader.GetReviews(&base.PullRequest{Number: 5, ForeignIndex: 186})
 	assert.NoError(t, err)
 	assertReviewsEqual(t, []*base.Review{
 		{
diff --git a/services/migrations/restore.go b/services/migrations/restore.go
index d30d90a6c4..8c9654a7e3 100644
--- a/services/migrations/restore.go
+++ b/services/migrations/restore.go
@@ -193,17 +193,13 @@ func (r *RepositoryRestorer) GetIssues(page, perPage int) ([]*base.Issue, bool,
 		}
 		return nil, false, err
 	}
-
-	for _, issue := range issues {
-		issue.Context = base.BasicIssueContext(issue.Number)
-	}
 	return issues, true, nil
 }
 
 // GetComments returns comments according issueNumber
-func (r *RepositoryRestorer) GetComments(opts base.GetCommentOptions) ([]*base.Comment, bool, error) {
+func (r *RepositoryRestorer) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
 	comments := make([]*base.Comment, 0, 10)
-	p := filepath.Join(r.commentDir(), fmt.Sprintf("%d.yml", opts.Context.ForeignID()))
+	p := filepath.Join(r.commentDir(), fmt.Sprintf("%d.yml", commentable.GetForeignIndex()))
 	_, err := os.Stat(p)
 	if err != nil {
 		if os.IsNotExist(err) {
@@ -247,15 +243,14 @@ func (r *RepositoryRestorer) GetPullRequests(page, perPage int) ([]*base.PullReq
 	}
 	for _, pr := range pulls {
 		pr.PatchURL = "file://" + filepath.Join(r.baseDir, pr.PatchURL)
-		pr.Context = base.BasicIssueContext(pr.Number)
 	}
 	return pulls, true, nil
 }
 
 // GetReviews returns pull requests review
-func (r *RepositoryRestorer) GetReviews(context base.IssueContext) ([]*base.Review, error) {
+func (r *RepositoryRestorer) GetReviews(reviewable base.Reviewable) ([]*base.Review, error) {
 	reviews := make([]*base.Review, 0, 10)
-	p := filepath.Join(r.reviewDir(), fmt.Sprintf("%d.yml", context.ForeignID()))
+	p := filepath.Join(r.reviewDir(), fmt.Sprintf("%d.yml", reviewable.GetForeignIndex()))
 	_, err := os.Stat(p)
 	if err != nil {
 		if os.IsNotExist(err) {