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>

models/fixtures/foreign_reference.yml

@@ -0,0 +1 @@
+[] # empty

models/foreignreference/error.go

@@ -0,0 +1,43 @@
+// Copyright 2022 Gitea. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package foreignreference
+
+import (
+	"fmt"
+)
+
+// ErrLocalIndexNotExist represents a "LocalIndexNotExist" kind of error.
+type ErrLocalIndexNotExist struct {
+	RepoID       int64
+	ForeignIndex int64
+	Type         string
+}
+
+// ErrLocalIndexNotExist checks if an error is a ErrLocalIndexNotExist.
+func IsErrLocalIndexNotExist(err error) bool {
+	_, ok := err.(ErrLocalIndexNotExist)
+	return ok
+}
+
+func (err ErrLocalIndexNotExist) Error() string {
+	return fmt.Sprintf("repository %d has no LocalIndex for ForeignIndex %d of type %s", err.RepoID, err.ForeignIndex, err.Type)
+}
+
+// ErrForeignIndexNotExist represents a "ForeignIndexNotExist" kind of error.
+type ErrForeignIndexNotExist struct {
+	RepoID     int64
+	LocalIndex int64
+	Type       string
+}
+
+// ErrForeignIndexNotExist checks if an error is a ErrForeignIndexNotExist.
+func IsErrForeignIndexNotExist(err error) bool {
+	_, ok := err.(ErrForeignIndexNotExist)
+	return ok
+}
+
+func (err ErrForeignIndexNotExist) Error() string {
+	return fmt.Sprintf("repository %d has no ForeignIndex for LocalIndex %d of type %s", err.RepoID, err.LocalIndex, err.Type)
+}

models/foreignreference/foreignreference.go

@@ -0,0 +1,32 @@
+// Copyright 2022 Gitea. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package foreignreference
+
+import (
+	"code.gitea.io/gitea/models/db"
+)
+
+// Type* are valid values for the Type field of ForeignReference
+const (
+	TypeIssue         = "issue"
+	TypePullRequest   = "pull_request"
+	TypeComment       = "comment"
+	TypeReview        = "review"
+	TypeReviewComment = "review_comment"
+	TypeRelease       = "release"
+)
+
+// ForeignReference represents external references
+type ForeignReference struct {
+	// RepoID is the first column in all indices. now we only need 2 indices: (repo, local) and (repo, foreign, type)
+	RepoID       int64  `xorm:"UNIQUE(repo_foreign_type) INDEX(repo_local)" `
+	LocalIndex   int64  `xorm:"INDEX(repo_local)"` // the resource key inside Gitea, it can be IssueIndex, or some model ID.
+	ForeignIndex string `xorm:"INDEX UNIQUE(repo_foreign_type)"`
+	Type         string `xorm:"VARCHAR(16) INDEX UNIQUE(repo_foreign_type)"`
+}
+
+func init() {
+	db.RegisterModel(new(ForeignReference))
+}

models/issue.go

@@ -15,6 +15,7 @@ import (
 
 	admin_model "code.gitea.io/gitea/models/admin"
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/foreignreference"
 	"code.gitea.io/gitea/models/issues"
 	"code.gitea.io/gitea/models/perm"
 	repo_model "code.gitea.io/gitea/models/repo"
@@ -72,6 +73,7 @@ type Issue struct {
 	Reactions        ReactionList                       `xorm:"-"`
 	TotalTrackedTime int64                              `xorm:"-"`
 	Assignees        []*user_model.User                 `xorm:"-"`
+	ForeignReference *foreignreference.ForeignReference `xorm:"-"`
 
 	// IsLocked limits commenting abilities to users on an issue
 	// with write access
@@ -271,6 +273,29 @@ func (issue *Issue) loadReactions(ctx context.Context) (err error) {
 	return nil
 }
 
+func (issue *Issue) loadForeignReference(ctx context.Context) (err error) {
+	if issue.ForeignReference != nil {
+		return nil
+	}
+	reference := &foreignreference.ForeignReference{
+		RepoID:     issue.RepoID,
+		LocalIndex: issue.Index,
+		Type:       foreignreference.TypeIssue,
+	}
+	has, err := db.GetEngine(ctx).Get(reference)
+	if err != nil {
+		return err
+	} else if !has {
+		return foreignreference.ErrForeignIndexNotExist{
+			RepoID:     issue.RepoID,
+			LocalIndex: issue.Index,
+			Type:       foreignreference.TypeIssue,
+		}
+	}
+	issue.ForeignReference = reference
+	return nil
+}
+
 func (issue *Issue) loadMilestone(e db.Engine) (err error) {
 	if (issue.Milestone == nil || issue.Milestone.ID != issue.MilestoneID) && issue.MilestoneID > 0 {
 		issue.Milestone, err = getMilestoneByRepoID(e, issue.RepoID, issue.MilestoneID)
@@ -332,6 +357,10 @@ func (issue *Issue) loadAttributes(ctx context.Context) (err error) {
 		}
 	}
 
+	if err = issue.loadForeignReference(ctx); err != nil && !foreignreference.IsErrForeignIndexNotExist(err) {
+		return err
+	}
+
 	return issue.loadReactions(ctx)
 }
 
@@ -1110,6 +1139,26 @@ func GetIssueByIndex(repoID, index int64) (*Issue, error) {
 	return issue, nil
 }
 
+// GetIssueByForeignIndex returns raw issue by foreign ID
+func GetIssueByForeignIndex(ctx context.Context, repoID, foreignIndex int64) (*Issue, error) {
+	reference := &foreignreference.ForeignReference{
+		RepoID:       repoID,
+		ForeignIndex: strconv.FormatInt(foreignIndex, 10),
+		Type:         foreignreference.TypeIssue,
+	}
+	has, err := db.GetEngine(ctx).Get(reference)
+	if err != nil {
+		return nil, err
+	} else if !has {
+		return nil, foreignreference.ErrLocalIndexNotExist{
+			RepoID:       repoID,
+			ForeignIndex: foreignIndex,
+			Type:         foreignreference.TypeIssue,
+		}
+	}
+	return GetIssueByIndex(repoID, reference.LocalIndex)
+}
+
 // GetIssueWithAttrsByIndex returns issue by index in a repository.
 func GetIssueWithAttrsByIndex(repoID, index int64) (*Issue, error) {
 	issue, err := GetIssueByIndex(repoID, index)

models/issue_test.go

@@ -8,11 +8,13 @@ import (
 	"context"
 	"fmt"
 	"sort"
+	"strconv"
 	"sync"
 	"testing"
 	"time"
 
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/foreignreference"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
@@ -534,3 +536,35 @@ func TestCorrectIssueStats(t *testing.T) {
 	assert.NoError(t, err)
 	assert.EqualValues(t, issueStats.OpenCount, issueAmount)
 }
+
+func TestIssueForeignReference(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	issue := unittest.AssertExistsAndLoadBean(t, &Issue{ID: 4}).(*Issue)
+	assert.NotEqualValues(t, issue.Index, issue.ID) // make sure they are different to avoid false positive
+
+	// it is fine for an issue to not have a foreign reference
+	err := issue.LoadAttributes()
+	assert.NoError(t, err)
+	assert.Nil(t, issue.ForeignReference)
+
+	var foreignIndex int64 = 12345
+	_, err = GetIssueByForeignIndex(context.Background(), issue.RepoID, foreignIndex)
+	assert.True(t, foreignreference.IsErrLocalIndexNotExist(err))
+
+	_, err = db.GetEngine(db.DefaultContext).Insert(&foreignreference.ForeignReference{
+		LocalIndex:   issue.Index,
+		ForeignIndex: strconv.FormatInt(foreignIndex, 10),
+		RepoID:       issue.RepoID,
+		Type:         foreignreference.TypeIssue,
+	})
+	assert.NoError(t, err)
+
+	err = issue.LoadAttributes()
+	assert.NoError(t, err)
+
+	assert.EqualValues(t, issue.ForeignReference.ForeignIndex, strconv.FormatInt(foreignIndex, 10))
+
+	found, err := GetIssueByForeignIndex(context.Background(), issue.RepoID, foreignIndex)
+	assert.NoError(t, err)
+	assert.EqualValues(t, found.Index, issue.Index)
+}

models/migrate.go

@@ -83,6 +83,13 @@ func insertIssue(ctx context.Context, issue *Issue) error {
 		}
 	}
 
+	if issue.ForeignReference != nil {
+		issue.ForeignReference.LocalIndex = issue.Index
+		if _, err := sess.Insert(issue.ForeignReference); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }
 

models/migrate_test.go

@@ -5,8 +5,10 @@
 package models
 
 import (
+	"strconv"
 	"testing"
 
+	"code.gitea.io/gitea/models/foreignreference"
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
@@ -45,6 +47,7 @@ func assertCreateIssues(t *testing.T, isPull bool) {
 		UserID: owner.ID,
 	}
 
+	foreignIndex := int64(12345)
 	title := "issuetitle1"
 	is := &Issue{
 		RepoID:      repo.ID,
@@ -58,11 +61,20 @@ func assertCreateIssues(t *testing.T, isPull bool) {
 		IsClosed:    true,
 		Labels:      []*Label{label},
 		Reactions:   []*Reaction{reaction},
+		ForeignReference: &foreignreference.ForeignReference{
+			ForeignIndex: strconv.FormatInt(foreignIndex, 10),
+			RepoID:       repo.ID,
+			Type:         foreignreference.TypeIssue,
+		},
 	}
 	err := InsertIssues(is)
 	assert.NoError(t, err)
 
 	i := unittest.AssertExistsAndLoadBean(t, &Issue{Title: title}).(*Issue)
+	assert.Nil(t, i.ForeignReference)
+	err = i.LoadAttributes()
+	assert.NoError(t, err)
+	assert.EqualValues(t, strconv.FormatInt(foreignIndex, 10), i.ForeignReference.ForeignIndex)
 	unittest.AssertExistsAndLoadBean(t, &Reaction{Type: "heart", UserID: owner.ID, IssueID: i.ID})
 }
 

models/migrations/migrations.go

@@ -373,6 +373,8 @@ var migrations = []Migration{
 	NewMigration("Increase WebAuthentication CredentialID size to 410 - NO-OPED", increaseCredentialIDTo410),
 	// v210 -> v211
 	NewMigration("v208 was completely broken - remigrate", remigrateU2FCredentials),
+	// v211 -> v212
+	NewMigration("Create ForeignReference table", createForeignReferenceTable),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v211.go

@@ -0,0 +1,26 @@
+// Copyright 2022 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 (
+	"fmt"
+
+	"xorm.io/xorm"
+)
+
+func createForeignReferenceTable(x *xorm.Engine) error {
+	type ForeignReference struct {
+		// RepoID is the first column in all indices. now we only need 2 indices: (repo, local) and (repo, foreign, type)
+		RepoID       int64  `xorm:"UNIQUE(repo_foreign_type) INDEX(repo_local)" `
+		LocalIndex   int64  `xorm:"INDEX(repo_local)"` // the resource key inside Gitea, it can be IssueIndex, or some model ID.
+		ForeignIndex string `xorm:"INDEX UNIQUE(repo_foreign_type)"`
+		Type         string `xorm:"VARCHAR(16) INDEX UNIQUE(repo_foreign_type)"`
+	}
+
+	if err := x.Sync2(new(ForeignReference)); err != nil {
+		return fmt.Errorf("Sync2: %v", err)
+	}
+	return nil
+}

modules/migration/comment.go

@@ -7,6 +7,13 @@ package migration
 
 import "time"
 
+// Commentable can be commented upon
+type Commentable interface {
+	GetLocalIndex() int64
+	GetForeignIndex() int64
+	GetContext() DownloaderContext
+}
+
 // Comment is a standard comment information
 type Comment struct {
 	IssueIndex  int64 `yaml:"issue_index"`

modules/migration/downloader.go

@@ -11,13 +11,6 @@ import (
 	"code.gitea.io/gitea/modules/structs"
 )
 
-// GetCommentOptions represents an options for get comment
-type GetCommentOptions struct {
-	Context  IssueContext
-	Page     int
-	PageSize int
-}
-
 // Downloader downloads the site repo information
 type Downloader interface {
 	SetContext(context.Context)
@@ -27,10 +20,11 @@ type Downloader interface {
 	GetReleases() ([]*Release, error)
 	GetLabels() ([]*Label, error)
 	GetIssues(page, perPage int) ([]*Issue, bool, error)
-	GetComments(opts GetCommentOptions) ([]*Comment, bool, error)
+	GetComments(commentable Commentable) ([]*Comment, bool, error)
+	GetAllComments(page, perPage int) ([]*Comment, bool, error)
 	SupportGetRepoComments() bool
 	GetPullRequests(page, perPage int) ([]*PullRequest, bool, error)
-	GetReviews(pullRequestContext IssueContext) ([]*Review, error)
+	GetReviews(reviewable Reviewable) ([]*Review, error)
 	FormatCloneURL(opts MigrateOptions, remoteAddr string) (string, error)
 }
 
@@ -39,3 +33,6 @@ type DownloaderFactory interface {
 	New(ctx context.Context, opts MigrateOptions) (Downloader, error)
 	GitServiceType() structs.GitServiceType
 }
+
+// DownloaderContext has opaque information only relevant to a given downloader
+type DownloaderContext interface{}

modules/migration/issue.go

@@ -7,25 +7,6 @@ package migration
 
 import "time"
 
-// IssueContext is used to map between local and foreign issue/PR ids.
-type IssueContext interface {
-	LocalID() int64
-	ForeignID() int64
-}
-
-// BasicIssueContext is a 1:1 mapping between local and foreign ids.
-type BasicIssueContext int64
-
-// LocalID gets the local id.
-func (c BasicIssueContext) LocalID() int64 {
-	return int64(c)
-}
-
-// ForeignID gets the foreign id.
-func (c BasicIssueContext) ForeignID() int64 {
-	return int64(c)
-}
-
 // Issue is a standard issue information
 type Issue struct {
 	Number       int64             `json:"number"`
@@ -44,7 +25,8 @@ type Issue struct {
 	Labels       []*Label          `json:"labels"`
 	Reactions    []*Reaction       `json:"reactions"`
 	Assignees    []string          `json:"assignees"`
-	Context     IssueContext `yaml:"-"`
+	ForeignIndex int64             `json:"foreign_id"`
+	Context      DownloaderContext `yaml:"-"`
 }
 
 // GetExternalName ExternalUserMigrated interface
@@ -52,3 +34,7 @@ func (i *Issue) GetExternalName() string { return i.PosterName }
 
 // GetExternalID ExternalUserMigrated interface
 func (i *Issue) GetExternalID() int64 { return i.PosterID }
+
+func (i *Issue) GetLocalIndex() int64          { return i.Number }
+func (i *Issue) GetForeignIndex() int64        { return i.ForeignIndex }
+func (i *Issue) GetContext() DownloaderContext { return i.Context }

modules/migration/null_downloader.go

@@ -47,18 +47,23 @@ func (n NullDownloader) GetIssues(page, perPage int) ([]*Issue, bool, error) {
 	return nil, false, &ErrNotSupported{Entity: "Issues"}
 }
 
-// GetComments returns comments according the options
-func (n NullDownloader) GetComments(GetCommentOptions) ([]*Comment, bool, error) {
+// GetComments returns comments of an issue or PR
+func (n NullDownloader) GetComments(commentable Commentable) ([]*Comment, bool, error) {
 	return nil, false, &ErrNotSupported{Entity: "Comments"}
 }
 
+// GetAllComments returns paginated comments
+func (n NullDownloader) GetAllComments(page, perPage int) ([]*Comment, bool, error) {
+	return nil, false, &ErrNotSupported{Entity: "AllComments"}
+}
+
 // GetPullRequests returns pull requests according page and perPage
 func (n NullDownloader) GetPullRequests(page, perPage int) ([]*PullRequest, bool, error) {
 	return nil, false, &ErrNotSupported{Entity: "PullRequests"}
 }
 
 // GetReviews returns pull requests review
-func (n NullDownloader) GetReviews(pullRequestContext IssueContext) ([]*Review, error) {
+func (n NullDownloader) GetReviews(reviewable Reviewable) ([]*Review, error) {
 	return nil, &ErrNotSupported{Entity: "Reviews"}
 }
 

modules/migration/pullrequest.go

@@ -35,9 +35,14 @@ type PullRequest struct {
 	Assignees      []string
 	IsLocked       bool `yaml:"is_locked"`
 	Reactions      []*Reaction
-	Context        IssueContext `yaml:"-"`
+	ForeignIndex   int64
+	Context        DownloaderContext `yaml:"-"`
 }
 
+func (p *PullRequest) GetLocalIndex() int64          { return p.Number }
+func (p *PullRequest) GetForeignIndex() int64        { return p.ForeignIndex }
+func (p *PullRequest) GetContext() DownloaderContext { return p.Context }
+
 // IsForkPullRequest returns true if the pull request from a forked repository but not the same repository
 func (p *PullRequest) IsForkPullRequest() bool {
 	return p.Head.RepoPath() != p.Base.RepoPath()

modules/migration/retry_downloader.go

@@ -148,7 +148,7 @@ func (d *RetryDownloader) GetIssues(page, perPage int) ([]*Issue, bool, error) {
 }
 
 // GetComments returns a repository's comments with retry
-func (d *RetryDownloader) GetComments(opts GetCommentOptions) ([]*Comment, bool, error) {
+func (d *RetryDownloader) GetComments(commentable Commentable) ([]*Comment, bool, error) {
 	var (
 		comments []*Comment
 		isEnd    bool
@@ -156,7 +156,7 @@ func (d *RetryDownloader) GetComments(opts GetCommentOptions) ([]*Comment, bool,
 	)
 
 	err = d.retry(func() error {
-		comments, isEnd, err = d.Downloader.GetComments(opts)
+		comments, isEnd, err = d.Downloader.GetComments(commentable)
 		return err
 	})
 
@@ -180,14 +180,14 @@ func (d *RetryDownloader) GetPullRequests(page, perPage int) ([]*PullRequest, bo
 }
 
 // GetReviews returns pull requests reviews
-func (d *RetryDownloader) GetReviews(pullRequestContext IssueContext) ([]*Review, error) {
+func (d *RetryDownloader) GetReviews(reviewable Reviewable) ([]*Review, error) {
 	var (
 		reviews []*Review
 		err     error
 	)
 
 	err = d.retry(func() error {
-		reviews, err = d.Downloader.GetReviews(pullRequestContext)
+		reviews, err = d.Downloader.GetReviews(reviewable)
 		return err
 	})
 

modules/migration/review.go

@@ -6,6 +6,12 @@ package migration
 
 import "time"
 
+// Reviewable can be reviewed
+type Reviewable interface {
+	GetLocalIndex() int64
+	GetForeignIndex() int64
+}
+
 // enumerate all review states
 const (
 	ReviewStatePending          = "PENDING"

services/migrations/codebase.go

@@ -266,19 +266,9 @@ 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
-}
-
 // GetIssues returns issues, limits are not supported
 // https://support.codebasehq.com/kb/tickets-and-milestones
 // https://support.codebasehq.com/kb/tickets-and-milestones/updating-tickets
@@ -402,9 +392,8 @@ 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:],
 			},
 		})
@@ -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
@@ -570,9 +559,8 @@ 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:],
 			},
 		})
@@ -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 {

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)
 }

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"}
-}

services/migrations/gitea_downloader.go

@@ -430,7 +430,7 @@ func (g *GiteaDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, err
 			Labels:       labels,
 			Assignees:    assignees,
 			IsLocked:     issue.IsLocked,
-			Context:     base.BasicIssueContext(issue.Index),
+			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,

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{
 		{

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 {

services/migrations/github.go

@@ -461,7 +461,7 @@ func (g *GithubDownloaderV3) GetIssues(page, perPage int) ([]*base.Issue, bool,
 			Closed:       issue.ClosedAt,
 			IsLocked:     issue.GetLocked(),
 			Assignees:    assignees,
-			Context:     base.BasicIssueContext(*issue.Number),
+			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)
+func (g *GithubDownloaderV3) GetComments(commentable base.Commentable) ([]*base.Comment, bool, error) {
+	comments, err := g.getComments(commentable)
 	return comments, false, err
 }
 
-	return g.GetAllComments(opts.Page, opts.PageSize)
-}
-
-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(),
@@ -711,7 +707,7 @@ func (g *GithubDownloaderV3) GetPullRequests(page, perPage int) ([]*base.PullReq
 			},
 			PatchURL:     pr.GetPatchURL(),
 			Reactions:    reactions,
-			Context:   base.BasicIssueContext(*pr.Number),
+			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)
 				}

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{
 		{

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) {
@@ -434,11 +424,8 @@ func (g *GitlabDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, er
 			Closed:       issue.ClosedAt,
 			IsLocked:     issue.DiscussionLocked,
 			Updated:      *issue.UpdatedAt,
-			Context: gitlabIssueContext{
-				foreignID:      int64(issue.IID),
-				localID:        int64(issue.IID),
-				IsMergeRequest: false,
-			},
+			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,
@@ -620,11 +607,8 @@ func (g *GitlabDownloader) GetPullRequests(page, perPage int) ([]*base.PullReque
 				OwnerName: pr.Author.Username,
 			},
 			PatchURL:     pr.WebURL + ".patch",
-			Context: gitlabIssueContext{
-				foreignID:      int64(pr.IID),
-				localID:        newPRNumber,
-				IsMergeRequest: true,
-			},
+			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,

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)
 	}

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,
@@ -300,7 +300,7 @@ func convertGogsIssue(issue *gogs.Issue) *base.Issue {
 		Updated:      issue.Updated,
 		Labels:       labels,
 		Closed:       closed,
-		Context:     base.BasicIssueContext(issue.Index),
+		ForeignIndex: issue.Index,
 	}
 }
 

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{
 		{

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
 			}

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 {
@@ -356,11 +346,8 @@ func (d *OneDevDownloader) GetIssues(page, perPage int) ([]*base.Issue, bool, er
 			Created:      issue.SubmitDate,
 			Updated:      issue.SubmitDate,
 			Labels:       []*base.Label{label},
-			Context: onedevIssueContext{
-				foreignID:     issue.ID,
-				localID:       issue.Number,
-				IsPullRequest: false,
-			},
+			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,

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{
 		{

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) {