Attempt to speed up pull request conflict checking

By skipping fetch from the head repository, and instead using the ref that
we already assume exists in the base repository.

Author: brechtvl

services/pull/check.go

@@ -357,7 +357,7 @@ func testPR(id int64) {
 		return
 	}
 
-	if err := TestPatch(pr); err != nil {
+	if err := TestPatch(pr, true); err != nil {
 		log.Error("testPatch[%-v]: %v", pr, err)
 		pr.Status = issues_model.PullRequestStatusError
 		if err := pr.UpdateCols("status"); err != nil {

services/pull/merge_prepare.go

@@ -45,7 +45,7 @@ func (ctx *mergeContext) RunOpts() *git.RunOpts {
 
 func createTemporaryRepoForMerge(ctx context.Context, pr *issues_model.PullRequest, doer *user_model.User, expectedHeadCommitID string) (mergeCtx *mergeContext, cancel context.CancelFunc, err error) {
 	// Clone base repo.
-	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr)
+	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr, false)
 	if err != nil {
 		log.Error("createTemporaryRepoForPR: %v", err)
 		return nil, cancel, err

services/pull/patch.go

@@ -58,12 +58,12 @@ var patchErrorSuffices = []string{
 }
 
 // TestPatch will test whether a simple patch will apply
-func TestPatch(pr *issues_model.PullRequest) error {
+func TestPatch(pr *issues_model.PullRequest, skipHeadRepoFetch bool) error {
 	ctx, _, finished := process.GetManager().AddContext(graceful.GetManager().HammerContext(), fmt.Sprintf("TestPatch: %s", pr))
 	defer finished()
 
 	// Clone base repo.
-	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr)
+	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr, skipHeadRepoFetch)
 	if err != nil {
 		log.Error("createTemporaryRepoForPR %-v: %v", pr, err)
 		return err

services/pull/pull.go

@@ -36,7 +36,7 @@ var pullWorkingPool = sync.NewExclusivePool()
 
 // NewPullRequest creates new pull request with labels for repository.
 func NewPullRequest(ctx context.Context, repo *repo_model.Repository, pull *issues_model.Issue, labelIDs []int64, uuids []string, pr *issues_model.PullRequest, assigneeIDs []int64) error {
-	if err := TestPatch(pr); err != nil {
+	if err := TestPatch(pr, false); err != nil {
 		return err
 	}
 
@@ -190,7 +190,7 @@ func ChangeTargetBranch(ctx context.Context, pr *issues_model.PullRequest, doer
 	pr.BaseBranch = targetBranch
 
 	// Refresh patch
-	if err := TestPatch(pr); err != nil {
+	if err := TestPatch(pr, false); err != nil {
 		return err
 	}
 
@@ -350,7 +350,7 @@ func AddTestPullRequestTask(doer *user_model.User, repoID int64, branch string,
 // checkIfPRContentChanged checks if diff to target branch has changed by push
 // A commit can be considered to leave the PR untouched if the patch/diff with its merge base is unchanged
 func checkIfPRContentChanged(ctx context.Context, pr *issues_model.PullRequest, oldCommitID, newCommitID string) (hasChanged bool, err error) {
-	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr)
+	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr, false)
 	if err != nil {
 		log.Error("CreateTemporaryRepoForPR %-v: %v", pr, err)
 		return false, err

services/pull/temp_repo.go

@@ -47,7 +47,7 @@ func (ctx *prContext) RunOpts() *git.RunOpts {
 
 // createTemporaryRepoForPR creates a temporary repo with "base" for pr.BaseBranch and "tracking" for  pr.HeadBranch
 // it also create a second base branch called "original_base"
-func createTemporaryRepoForPR(ctx context.Context, pr *issues_model.PullRequest) (prCtx *prContext, cancel context.CancelFunc, err error) {
+func createTemporaryRepoForPR(ctx context.Context, pr *issues_model.PullRequest, skipHeadRepoFetch bool) (prCtx *prContext, cancel context.CancelFunc, err error) {
 	if err := pr.LoadHeadRepo(ctx); err != nil {
 		log.Error("%-v LoadHeadRepo: %v", pr, err)
 		return nil, nil, fmt.Errorf("%v LoadHeadRepo: %w", pr, err)
@@ -171,7 +171,15 @@ func createTemporaryRepoForPR(ctx context.Context, pr *issues_model.PullRequest)
 	// Fetch head branch
 	var headBranch string
 	if pr.Flow == issues_model.PullRequestFlowGithub {
-		headBranch = git.BranchPrefix + pr.HeadBranch
+		if skipHeadRepoFetch {
+			// Blender: for conflict checking on changes to the base branch, skip slow
+			// fetching from the head repository and instead use the ref that already
+			// exists in the base repository.
+			headBranch = pr.GetGitRefName()
+			remoteRepoName = "origin"
+		} else {
+			headBranch = git.BranchPrefix + pr.HeadBranch
+		}
 	} else if len(pr.HeadCommitID) == git.SHAFullLength { // for not created pull request
 		headBranch = pr.HeadCommitID
 	} else {

services/pull/update.go

@@ -166,7 +166,7 @@ func IsUserAllowedToUpdate(ctx context.Context, pull *issues_model.PullRequest,
 // GetDiverging determines how many commits a PR is ahead or behind the PR base branch
 func GetDiverging(ctx context.Context, pr *issues_model.PullRequest) (*git.DivergeObject, error) {
 	log.Trace("GetDiverging[%-v]: compare commits", pr)
-	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr)
+	prCtx, cancel, err := createTemporaryRepoForPR(ctx, pr, false)
 	if err != nil {
 		if !models.IsErrBranchDoesNotExist(err) {
 			log.Error("CreateTemporaryRepoForPR %-v: %v", pr, err)

templates/repo/issue/view_title.tmpl

@@ -98,7 +98,7 @@
 								</div>
 							</div>
 						</div>
-				    <div class="desc"><br/>When changing the target branch, be careful to rebase the branch in your fork to match. See <a href="https://wiki.blender.org/wiki/Tools/Pull_Requests">documentation</a>.</div>
+						<div class="desc"><br/>When changing the target branch, be careful to rebase the branch in your fork to match. See <a href="https://wiki.blender.org/wiki/Tools/Pull_Requests">documentation</a>.</div>
 					</span>
 				{{end}}
 			{{else}}