feat: [CODE-1474]: add check PR rebaseability (#2763)

* update migration number
* rename UpdateConflict->UpdateMergeOutcome
* small fixes
* handle mergeability for all merge methods
* alway separate rebaseability check
* add check PR rebaseability

app/api/controller/pullreq/merge.go

@@ -58,14 +58,16 @@ func (in *MergeInput) sanitize() error {
 		return usererror.BadRequest("source SHA must be provided")
 	}
 
-	if in.Method != "" {
+	if in.Method == "" {
+		in.Method = enum.MergeMethodMerge
+	}
+
 	method, ok := in.Method.Sanitize()
 	if !ok {
 		return usererror.BadRequestf("unsupported merge method: %s", in.Method)
 	}
 
 	in.Method = method
-	}
 
 	// cleanup title / message (NOTE: git doesn't support white space only)
 	in.Title = strings.TrimSpace(in.Title)
@@ -233,17 +235,44 @@ func (c *Controller) Merge(
 		// has advanced. It's possible that the merge base commit is different too.
 		// So, the next time the API gets called for the same PR the mergeability status will not be unchecked.
 		// Without dry-run the execution would proceed below and would either merge the PR or set the conflict status.
-		if pr.MergeCheckStatus == enum.MergeCheckStatusUnchecked {
+
-			mergeOutput, err := c.git.Merge(ctx, &git.MergeParams{
+		var mergeOutput git.MergeOutput
+
+		// We distinguish two types when checking mergeability: Rebase and Non-Rebase.
+		// * Merge methods Merge and Squash will always have the same results.
+		// * Merge method Rebase is special because it must always check all commits, one at a time.
+		// * Merge method Fast-Forward can never have conflicts,
+		//   but for it the merge base SHA must be equal to target branch SHA.
+		// The result of the tests will be stored (think cached) in the database for these two types
+		// in the fields merge_check_status and rebase_check_status.
+
+		checkMergeability := func(method enum.MergeMethod) bool {
+			switch method {
+			case enum.MergeMethodMerge, enum.MergeMethodSquash:
+				return pr.MergeCheckStatus == enum.MergeCheckStatusUnchecked
+			case enum.MergeMethodRebase:
+				return pr.RebaseCheckStatus == enum.MergeCheckStatusUnchecked
+			case enum.MergeMethodFastForward:
+				// Always check for ff merge. There can never be conflicts,
+				// but we are interested in if it returns the conflict error and merge-output data.
+				return true
+			default:
+				return true // should not happen
+			}
+		}(in.Method)
+
+		if checkMergeability {
+			mergeOutput, err = c.git.Merge(ctx, &git.MergeParams{
 				WriteParams:     targetWriteParams,
 				BaseBranch:      pr.TargetBranch,
 				HeadRepoUID:     sourceRepo.GitUID,
 				HeadBranch:      pr.SourceBranch,
 				RefType:         gitenum.RefTypeUndefined, // update no refs -> no commit will be created
 				HeadExpectedSHA: sha.Must(in.SourceSHA),
+				Method:          gitenum.MergeMethod(in.Method),
 			})
 			if err != nil {
-				return nil, nil, fmt.Errorf("merge check execution failed: %w", err)
+				return nil, nil, fmt.Errorf("failed merge check with method=%s: %w", in.Method, err)
 			}
 
 			pr, err = c.pullreqStore.UpdateOptLock(ctx, pr, func(pr *types.PullReq) error {
@@ -255,25 +284,19 @@ func (c *Controller) Merge(
 					return usererror.BadRequest("Pull request must be open")
 				}
 
-				if len(mergeOutput.ConflictFiles) > 0 {
-					pr.MergeCheckStatus = enum.MergeCheckStatusConflict
-					pr.MergeBaseSHA = mergeOutput.MergeBaseSHA.String()
-					pr.MergeTargetSHA = ptr.String(mergeOutput.BaseSHA.String())
-					pr.MergeSHA = nil
-					pr.MergeConflicts = mergeOutput.ConflictFiles
-				} else {
-					pr.MergeCheckStatus = enum.MergeCheckStatusMergeable
 				pr.MergeBaseSHA = mergeOutput.MergeBaseSHA.String()
 				pr.MergeTargetSHA = ptr.String(mergeOutput.BaseSHA.String())
 				pr.MergeSHA = nil // dry-run doesn't create a merge commit so output is empty.
-					pr.MergeConflicts = nil
+
-				}
+				pr.UpdateMergeOutcome(in.Method, mergeOutput.ConflictFiles)
+
 				pr.Stats.DiffStats = types.NewDiffStats(
 					mergeOutput.CommitCount,
 					mergeOutput.ChangedFileCount,
 					mergeOutput.Additions,
 					mergeOutput.Deletions,
 				)
+
 				return nil
 			})
 			if err != nil {
@@ -286,6 +309,13 @@ func (c *Controller) Merge(
 			}
 		}
 
+		var conflicts []string
+		if in.Method == enum.MergeMethodRebase {
+			conflicts = pr.RebaseConflicts
+		} else {
+			conflicts = pr.MergeConflicts
+		}
+
 		// With in.DryRun=true this function never returns types.MergeViolations
 		out := &types.MergeResponse{
 			BranchDeleted:  ruleOut.DeleteSourceBranch,
@@ -293,7 +323,8 @@ func (c *Controller) Merge(
 
 			// values only returned by dry run
 			DryRun:                              true,
-			ConflictFiles:                       pr.MergeConflicts,
+			Mergeable:                           len(conflicts) == 0,
+			ConflictFiles:                       conflicts,
 			AllowedMethods:                      ruleOut.AllowedMethods,
 			RequiresCodeOwnersApproval:          ruleOut.RequiresCodeOwnersApproval,
 			RequiresCodeOwnersApprovalLatest:    ruleOut.RequiresCodeOwnersApprovalLatest,
@@ -399,11 +430,10 @@ func (c *Controller) Merge(
 			}
 
 			// update all Merge specific information
-			pr.MergeCheckStatus = enum.MergeCheckStatusConflict
 			pr.MergeBaseSHA = mergeOutput.MergeBaseSHA.String()
 			pr.MergeTargetSHA = ptr.String(mergeOutput.BaseSHA.String())
 			pr.MergeSHA = nil
-			pr.MergeConflicts = mergeOutput.ConflictFiles
+			pr.UpdateMergeOutcome(in.Method, mergeOutput.ConflictFiles)
 			pr.Stats.DiffStats = types.NewDiffStats(
 				mergeOutput.CommitCount,
 				mergeOutput.ChangedFileCount,
@@ -447,12 +477,11 @@ func (c *Controller) Merge(
 
 		// update all Merge specific information (might be empty if previous merge check failed)
 		// since this is the final operation on the PR, we update any sha that might've changed by now.
-		pr.MergeCheckStatus = enum.MergeCheckStatusMergeable
 		pr.SourceSHA = mergeOutput.HeadSHA.String()
 		pr.MergeTargetSHA = ptr.String(mergeOutput.BaseSHA.String())
 		pr.MergeBaseSHA = mergeOutput.MergeBaseSHA.String()
 		pr.MergeSHA = ptr.String(mergeOutput.MergeSHA.String())
-		pr.MergeConflicts = nil
+		pr.MarkAsMerged()
 		pr.Stats.DiffStats = types.NewDiffStats(
 			mergeOutput.CommitCount,
 			mergeOutput.ChangedFileCount,

app/api/controller/pullreq/pr_create.go

@@ -202,9 +202,10 @@ func newPullReq(
 		ActivitySeq:       0,
 		MergedBy:          nil,
 		Merged:            nil,
-		MergeCheckStatus: enum.MergeCheckStatusUnchecked,
 		MergeMethod:       nil,
 		MergeBaseSHA:      mergeBaseSHA.String(),
+		MergeCheckStatus:  enum.MergeCheckStatusUnchecked,
+		RebaseCheckStatus: enum.MergeCheckStatusUnchecked,
 		Author:            *session.Principal.ToPrincipalInfo(),
 		Merger:            nil,
 	}

app/api/controller/pullreq/pr_state.go

@@ -146,11 +146,11 @@ func (c *Controller) State(ctx context.Context,
 			nowMilli := time.Now().UnixMilli()
 
 			// clear all merge (check) related fields
-			pr.MergeCheckStatus = enum.MergeCheckStatusUnchecked
 			pr.MergeSHA = nil
-			pr.MergeConflicts = nil
 			pr.MergeTargetSHA = nil
 			pr.Closed = &nowMilli
+			pr.MarkAsMergeUnchecked()
+
 		case changeReopen:
 			pr.SourceSHA = sourceSHA.String()
 			pr.MergeBaseSHA = mergeBaseSHA.String()

app/services/migrate/pullreq.go

@@ -277,12 +277,11 @@ func (r *repoImportState) convertPullReq(
 		mergeMethod := enum.MergeMethodMerge // Don't know
 		pr.MergeMethod = &mergeMethod
 
-		pr.MergeCheckStatus = enum.MergeCheckStatusMergeable
 		pr.SourceSHA = extPullReq.Head.SHA
 		pr.MergeTargetSHA = &extPullReq.Base.SHA
 		pr.MergeBaseSHA = extPullReq.Base.SHA
 		pr.MergeSHA = nil // Don't have this.
-		pr.MergeConflicts = nil
+		pr.MarkAsMerged()
 
 	case enum.PullReqStateClosed:
 		// For closed PR's it's not important to verify existence of branches and commits.
@@ -290,10 +289,11 @@ func (r *repoImportState) convertPullReq(
 		pr.SourceSHA = extPullReq.Head.SHA
 		pr.MergeTargetSHA = &extPullReq.Base.SHA
 		pr.MergeBaseSHA = extPullReq.Base.SHA
-		pr.MergeCheckStatus = enum.MergeCheckStatusUnchecked
 		pr.MergeSHA = nil
 		pr.MergeConflicts = nil
 		pr.MergeTargetSHA = nil
+		pr.MarkAsMergeUnchecked()
+
 		pr.Closed = &pr.Updated
 
 	case enum.PullReqStateOpen:
@@ -330,7 +330,7 @@ func (r *repoImportState) convertPullReq(
 		pr.SourceSHA = sourceSHA
 		pr.MergeTargetSHA = &targetSHA
 		pr.MergeBaseSHA = mergeBase.MergeBaseSHA.String()
-		pr.MergeCheckStatus = enum.MergeCheckStatusUnchecked
+		pr.MarkAsMergeUnchecked()
 	}
 
 	log.Debug().Str("pullreq.state", string(pr.State)).Msg("importing pull request")

app/services/pullreq/handlers_branch.go

@@ -122,11 +122,11 @@ func (s *Service) triggerPREventOnBranchUpdate(ctx context.Context,
 			pr.MergeBaseSHA = newMergeBase.String()
 
 			// reset merge-check fields for new run
-			pr.MergeCheckStatus = enum.MergeCheckStatusUnchecked
+
 			pr.MergeSHA = nil
-			pr.MergeConflicts = nil
 			pr.Stats.DiffStats.Commits = nil
 			pr.Stats.DiffStats.FilesChanged = nil
+			pr.MarkAsMergeUnchecked()
 
 			return nil
 		})
@@ -198,9 +198,8 @@ func (s *Service) closePullReqOnBranchDelete(ctx context.Context,
 			activitySeqPRClosed = pr.ActivitySeq
 
 			pr.State = enum.PullReqStateClosed
-			pr.MergeCheckStatus = enum.MergeCheckStatusUnchecked
 			pr.MergeSHA = nil
-			pr.MergeConflicts = nil
+			pr.MarkAsMergeUnchecked()
 
 			return nil
 		})

app/services/pullreq/handlers_mergeable.go

@@ -221,19 +221,14 @@ func (s *Service) updateMergeData(
 			return events.NewDiscardEventErrorf("PR SHA %s is newer than %s", pr.SourceSHA, newSHA)
 		}
 
-		if len(mergeOutput.ConflictFiles) > 0 {
-			pr.MergeCheckStatus = enum.MergeCheckStatusConflict
 		pr.MergeBaseSHA = mergeOutput.MergeBaseSHA.String()
 		pr.MergeTargetSHA = ptr.String(mergeOutput.BaseSHA.String())
+		if mergeOutput.MergeSHA.IsEmpty() {
 			pr.MergeSHA = nil
-			pr.MergeConflicts = mergeOutput.ConflictFiles
 		} else {
-			pr.MergeCheckStatus = enum.MergeCheckStatusMergeable
-			pr.MergeBaseSHA = mergeOutput.MergeBaseSHA.String()
-			pr.MergeTargetSHA = ptr.String(mergeOutput.BaseSHA.String())
 			pr.MergeSHA = ptr.String(mergeOutput.MergeSHA.String())
-			pr.MergeConflicts = nil
 		}
+		pr.UpdateMergeOutcome(enum.MergeMethodMerge, mergeOutput.ConflictFiles)
 		pr.Stats.DiffStats = types.NewDiffStats(
 			mergeOutput.CommitCount,
 			mergeOutput.ChangedFileCount,

app/store/database/migrate/postgres/0080_alter_table_pullreq_add_rebaseability.down.sql

@@ -0,0 +1,3 @@
+ALTER TABLE pullreqs
+    DROP COLUMN pullreq_rebase_conflicts,
+    DROP COLUMN pullreq_rebase_check_status;

app/store/database/migrate/postgres/0080_alter_table_pullreq_add_rebaseability.up.sql

@@ -0,0 +1,3 @@
+ALTER TABLE pullreqs
+    ADD COLUMN pullreq_rebase_check_status TEXT NOT NULL DEFAULT 'unchecked',
+    ADD COLUMN pullreq_rebase_conflicts TEXT;

app/store/database/migrate/sqlite/0080_alter_table_pullreq_add_rebaseability.down.sql

@@ -0,0 +1,2 @@
+ALTER TABLE pullreqs DROP COLUMN pullreq_rebase_conflicts;
+ALTER TABLE pullreqs DROP COLUMN pullreq_rebase_check_status;

app/store/database/migrate/sqlite/0080_alter_table_pullreq_add_rebaseability.up.sql

@@ -0,0 +1,2 @@
+ALTER TABLE pullreqs ADD COLUMN pullreq_rebase_check_status TEXT NOT NULL DEFAULT 'unchecked';
+ALTER TABLE pullreqs ADD COLUMN pullreq_rebase_conflicts TEXT;

app/store/database/pullreq.go

@@ -85,11 +85,14 @@ type pullReq struct {
 	Merged      null.Int    `db:"pullreq_merged"`
 	MergeMethod null.String `db:"pullreq_merge_method"`
 
-	MergeCheckStatus enum.MergeCheckStatus `db:"pullreq_merge_check_status"`
 	MergeTargetSHA null.String `db:"pullreq_merge_target_sha"`
 	MergeBaseSHA   string      `db:"pullreq_merge_base_sha"`
 	MergeSHA       null.String `db:"pullreq_merge_sha"`
+
+	MergeCheckStatus  enum.MergeCheckStatus `db:"pullreq_merge_check_status"`
 	MergeConflicts    null.String           `db:"pullreq_merge_conflicts"`
+	RebaseCheckStatus enum.MergeCheckStatus `db:"pullreq_rebase_check_status"`
+	RebaseConflicts   null.String           `db:"pullreq_rebase_conflicts,omitempty"`
 
 	CommitCount null.Int `db:"pullreq_commit_count"`
 	FileCount   null.Int `db:"pullreq_file_count"`
@@ -121,11 +124,13 @@ const (
 		,pullreq_merged_by
 		,pullreq_merged
 		,pullreq_merge_method
-		,pullreq_merge_check_status
 		,pullreq_merge_target_sha
 		,pullreq_merge_base_sha
 		,pullreq_merge_sha
+		,pullreq_merge_check_status
 		,pullreq_merge_conflicts
+		,pullreq_rebase_check_status
+		,pullreq_rebase_conflicts
 		,pullreq_commit_count
 		,pullreq_file_count
 		,pullreq_additions
@@ -218,11 +223,13 @@ func (s *PullReqStore) Create(ctx context.Context, pr *types.PullReq) error {
 		,pullreq_merged_by
 		,pullreq_merged
 		,pullreq_merge_method
-		,pullreq_merge_check_status
 		,pullreq_merge_target_sha
 		,pullreq_merge_base_sha
 		,pullreq_merge_sha
+		,pullreq_merge_check_status
 		,pullreq_merge_conflicts
+		,pullreq_rebase_check_status
+		,pullreq_rebase_conflicts
 		,pullreq_commit_count
 		,pullreq_file_count
 		,pullreq_additions
@@ -250,11 +257,13 @@ func (s *PullReqStore) Create(ctx context.Context, pr *types.PullReq) error {
 		,:pullreq_merged_by
 		,:pullreq_merged
 		,:pullreq_merge_method
-		,:pullreq_merge_check_status
 		,:pullreq_merge_target_sha
 		,:pullreq_merge_base_sha
 		,:pullreq_merge_sha
+		,:pullreq_merge_check_status
 		,:pullreq_merge_conflicts
+		,:pullreq_rebase_check_status
+		,:pullreq_rebase_conflicts
 		,:pullreq_commit_count
 		,:pullreq_file_count
 		,:pullreq_additions
@@ -295,11 +304,13 @@ func (s *PullReqStore) Update(ctx context.Context, pr *types.PullReq) error {
 		,pullreq_merged_by = :pullreq_merged_by
 		,pullreq_merged = :pullreq_merged
 		,pullreq_merge_method = :pullreq_merge_method
-		,pullreq_merge_check_status = :pullreq_merge_check_status
 		,pullreq_merge_target_sha = :pullreq_merge_target_sha
 		,pullreq_merge_base_sha = :pullreq_merge_base_sha
 		,pullreq_merge_sha = :pullreq_merge_sha
+		,pullreq_merge_check_status = :pullreq_merge_check_status
 		,pullreq_merge_conflicts = :pullreq_merge_conflicts
+		,pullreq_rebase_check_status = :pullreq_rebase_check_status
+		,pullreq_rebase_conflicts = :pullreq_rebase_conflicts
 		,pullreq_commit_count = :pullreq_commit_count
 		,pullreq_file_count = :pullreq_file_count
 		,pullreq_additions = :pullreq_additions
@@ -387,10 +398,12 @@ func (s *PullReqStore) ResetMergeCheckStatus(
 	SET
 		 pullreq_updated = $1
 		,pullreq_version = pullreq_version + 1
-		,pullreq_merge_check_status = $2
 		,pullreq_merge_target_sha = NULL
 		,pullreq_merge_sha = NULL
+		,pullreq_merge_check_status = $2
 		,pullreq_merge_conflicts = NULL
+		,pullreq_rebase_check_status = $2
+		,pullreq_rebase_conflicts = NULL
 		,pullreq_commit_count = NULL
 		,pullreq_file_count = NULL
 		,pullreq_additions = NULL
@@ -703,10 +716,13 @@ func (s *PullReqStore) applyFilter(stmt *squirrel.SelectBuilder, opts *types.Pul
 }
 
 func mapPullReq(pr *pullReq) *types.PullReq {
-	var mergeConflicts []string
+	var mergeConflicts, rebaseConflicts []string
 	if pr.MergeConflicts.Valid {
 		mergeConflicts = strings.Split(pr.MergeConflicts.String, "\n")
 	}
+	if pr.RebaseConflicts.Valid {
+		rebaseConflicts = strings.Split(pr.RebaseConflicts.String, "\n")
+	}
 
 	return &types.PullReq{
 		ID:                pr.ID,
@@ -737,6 +753,8 @@ func mapPullReq(pr *pullReq) *types.PullReq {
 		MergeBaseSHA:      pr.MergeBaseSHA,
 		MergeSHA:          pr.MergeSHA.Ptr(),
 		MergeConflicts:    mergeConflicts,
+		RebaseCheckStatus: pr.RebaseCheckStatus,
+		RebaseConflicts:   rebaseConflicts,
 		Author:            types.PrincipalInfo{},
 		Merger:            nil,
 		Stats: types.PullReqStats{
@@ -754,6 +772,7 @@ func mapPullReq(pr *pullReq) *types.PullReq {
 
 func mapInternalPullReq(pr *types.PullReq) *pullReq {
 	mergeConflicts := strings.Join(pr.MergeConflicts, "\n")
+	rebaseConflicts := strings.Join(pr.RebaseConflicts, "\n")
 	m := &pullReq{
 		ID:                pr.ID,
 		Version:           pr.Version,
@@ -783,6 +802,8 @@ func mapInternalPullReq(pr *types.PullReq) *pullReq {
 		MergeBaseSHA:      pr.MergeBaseSHA,
 		MergeSHA:          null.StringFromPtr(pr.MergeSHA),
 		MergeConflicts:    null.NewString(mergeConflicts, mergeConflicts != ""),
+		RebaseCheckStatus: pr.RebaseCheckStatus,
+		RebaseConflicts:   null.NewString(rebaseConflicts, rebaseConflicts != ""),
 		CommitCount:       null.IntFromPtr(pr.Stats.Commits),
 		FileCount:         null.IntFromPtr(pr.Stats.FilesChanged),
 		Additions:         null.IntFromPtr(pr.Stats.Additions),

git/merge.go

@@ -26,8 +26,6 @@ import (
 	"github.com/harness/gitness/git/hook"
 	"github.com/harness/gitness/git/merge"
 	"github.com/harness/gitness/git/sha"
-
-	"github.com/rs/zerolog/log"
 )
 
 // MergeParams is input structure object for merging operation.
@@ -172,16 +170,6 @@ func (s *Service) Merge(ctx context.Context, params *MergeParams) (MergeOutput,
 		}
 	}
 
-	// logger
-
-	log := log.Ctx(ctx).With().
-		Str("repo_uid", params.RepoUID).
-		Str("head", params.HeadBranch).
-		Str("base", params.BaseBranch).
-		Str("method", string(mergeMethod)).
-		Str("ref", refPath).
-		Logger()
-
 	// find the commit SHAs
 
 	baseCommitSHA, err := s.git.GetFullCommitID(ctx, repoPath, params.BaseBranch)
@@ -225,35 +213,6 @@ func (s *Service) Merge(ctx context.Context, params *MergeParams) (MergeOutput,
 		return MergeOutput{}, fmt.Errorf("failed to find commit count for merge check: %w", err)
 	}
 
-	// handle simple merge check
-
-	if params.RefType == enum.RefTypeUndefined && params.Method != enum.MergeMethodRebase {
-		// Merge method rebase can result in conflicts even if other methods do not.
-		// This is because commits are rebased one by one. And this is why for other merge method we just return
-		// list of conflicts, but for rebase we proceed with the rebasing (even if no ref would be updated).
-
-		_, _, conflicts, err := merge.FindConflicts(ctx, repoPath, baseCommitSHA.String(), headCommitSHA.String())
-		if err != nil {
-			return MergeOutput{}, errors.Internal(err,
-				"Merge check failed to find conflicts between commits %s and %s",
-				baseCommitSHA.String(), headCommitSHA.String())
-		}
-
-		log.Debug().Msg("merged check completed")
-
-		return MergeOutput{
-			BaseSHA:          baseCommitSHA,
-			HeadSHA:          headCommitSHA,
-			MergeBaseSHA:     mergeBaseCommitSHA,
-			MergeSHA:         sha.None,
-			CommitCount:      commitCount,
-			ChangedFileCount: shortStat.Files,
-			Additions:        shortStat.Additions,
-			Deletions:        shortStat.Deletions,
-			ConflictFiles:    conflicts,
-		}, nil
-	}
-
 	// author and committer
 
 	now := time.Now().UTC()

types/pullreq.go

@@ -51,11 +51,14 @@ type PullReq struct {
 	Merged      *int64            `json:"merged"`
 	MergeMethod *enum.MergeMethod `json:"merge_method"`
 
-	MergeCheckStatus enum.MergeCheckStatus `json:"merge_check_status"`
 	MergeTargetSHA *string `json:"merge_target_sha"`
 	MergeBaseSHA   string  `json:"merge_base_sha"`
 	MergeSHA       *string `json:"-"` // TODO: either remove or ensure it's being set (merge dry-run)
+
+	MergeCheckStatus  enum.MergeCheckStatus `json:"merge_check_status"`
 	MergeConflicts    []string              `json:"merge_conflicts,omitempty"`
+	RebaseCheckStatus enum.MergeCheckStatus `json:"rebase_check_status"`
+	RebaseConflicts   []string              `json:"rebase_conflicts,omitempty"`
 
 	Author PrincipalInfo  `json:"author"`
 	Merger *PrincipalInfo `json:"merger"`
@@ -64,6 +67,53 @@ type PullReq struct {
 	Labels []*LabelPullReqAssignmentInfo `json:"labels,omitempty"`
 }
 
+func (pr *PullReq) UpdateMergeOutcome(method enum.MergeMethod, conflictFiles []string) {
+	switch method {
+	case enum.MergeMethodMerge, enum.MergeMethodSquash:
+		if len(conflictFiles) > 0 {
+			pr.MergeCheckStatus = enum.MergeCheckStatusConflict
+			pr.MergeConflicts = conflictFiles
+		} else {
+			pr.MergeCheckStatus = enum.MergeCheckStatusMergeable
+			pr.MergeConflicts = nil
+		}
+	case enum.MergeMethodRebase:
+		if len(conflictFiles) > 0 {
+			pr.RebaseCheckStatus = enum.MergeCheckStatusConflict
+			pr.RebaseConflicts = conflictFiles
+		} else {
+			pr.RebaseCheckStatus = enum.MergeCheckStatusMergeable
+			pr.RebaseConflicts = nil
+		}
+	case enum.MergeMethodFastForward:
+		// fast-forward merge can't have conflicts
+	}
+}
+
+func (pr *PullReq) MarkAsMergeUnchecked() {
+	pr.MergeCheckStatus = enum.MergeCheckStatusUnchecked
+	pr.MergeConflicts = nil
+	pr.RebaseCheckStatus = enum.MergeCheckStatusUnchecked
+	pr.RebaseConflicts = nil
+}
+
+func (pr *PullReq) MarkAsMergeable() {
+	pr.MergeCheckStatus = enum.MergeCheckStatusMergeable
+	pr.MergeConflicts = nil
+}
+
+func (pr *PullReq) MarkAsRebaseable() {
+	pr.RebaseCheckStatus = enum.MergeCheckStatusMergeable
+	pr.RebaseConflicts = nil
+}
+
+func (pr *PullReq) MarkAsMerged() {
+	pr.MergeCheckStatus = enum.MergeCheckStatusMergeable
+	pr.MergeConflicts = nil
+	pr.RebaseCheckStatus = enum.MergeCheckStatusMergeable
+	pr.RebaseConflicts = nil
+}
+
 // DiffStats shows total number of commits and modified files.
 type DiffStats struct {
 	Commits      *int64 `json:"commits,omitempty"`
@@ -201,6 +251,7 @@ type MergeResponse struct {
 
 	// values only returned on dryrun
 	DryRun                              bool               `json:"dry_run,omitempty"`
+	Mergeable                           bool               `json:"mergeable,omitempty"`
 	ConflictFiles                       []string           `json:"conflict_files,omitempty"`
 	AllowedMethods                      []enum.MergeMethod `json:"allowed_methods,omitempty"`
 	MinimumRequiredApprovalsCount       int                `json:"minimum_required_approvals_count,omitempty"`