Use GraphQL UpdatePullRequestBranch mutation for conflict-free branch updates (#8419)

* Initial plan

* Use GraphQL UpdatePullRequestBranch mutation when there are no conflicts

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Use explicit mergeable state check for GraphQL branch update

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Add validation for head SHA and clarify handling of all mergeable states

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Show update branch button when PR is not checked out (no conflicts)

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Check for conflicts in isUpdateBranchWithGitHubEnabled

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Revert proposed changes

* Pull local branch after GraphQL update when PR is checked out

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Only pull after GraphQL update, not after REST API conflict resolution

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Clean up

* Revert api files

* Update string

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/github/folderRepositoryManager.ts

@@ -2453,6 +2453,7 @@ export class FolderRepositoryManager extends Disposable {
 		}
 
 		const isBrowser = (vscode.env.appHost === 'vscode.dev' || vscode.env.appHost === 'github.dev');
+
 		if (!pullRequest.isActive || isBrowser) {
 			const conflictModel = await vscode.window.withProgress({ location: vscode.ProgressLocation.Notification, title: vscode.l10n.t('Finding conflicts...') }, () => createConflictResolutionModel(pullRequest));
 			if (conflictModel === undefined) {
@@ -2474,6 +2475,21 @@ export class FolderRepositoryManager extends Disposable {
 			}
 		}
 
+		if (pullRequest.item.mergeable !== PullRequestMergeability.Conflict) {
+			const result = await vscode.window.withProgress(
+				{ location: vscode.ProgressLocation.Notification, title: vscode.l10n.t('Updating branch...') },
+				async () => {
+					const success = await pullRequest.updateBranchWithGraphQL();
+					if (success && pullRequest.isActive) {
+						await this.repository.pull();
+					}
+					return success;
+				}
+			);
+			return result;
+		}
+
+
 		if (this.repository.state.workingTreeChanges.length > 0 || this.repository.state.indexChanges.length > 0) {
 			await vscode.window.showErrorMessage(vscode.l10n.t('The pull request branch cannot be updated when the there changed files in the working tree or index. Stash or commit all change and then try again.'), { modal: true });
 			return false;
@@ -3053,7 +3069,7 @@ export const byRemoteName = (name: string): Predicate<GitHubRepository> => ({ re
 /**
  * Unwraps lines that were wrapped for conventional commit message formatting (typically at 72 characters).
  * Similar to GitHub's behavior when converting commit messages to PR descriptions.
- * 
+ *
  * Rules:
  * - Preserves blank lines as paragraph breaks
  * - Preserves fenced code blocks (```)

src/github/graphql.ts

@@ -545,6 +545,15 @@ export interface EnqueuePullRequestResponse {
 	}
 }
 
+export interface UpdatePullRequestBranchResponse {
+	updatePullRequestBranch: {
+		pullRequest: {
+			id: string;
+			headRefOid: string;
+		}
+	}
+}
+
 export interface SubmittedReview extends Review {
 	comments: {
 		nodes: ReviewComment[];

src/github/pullRequestModel.ts

@@ -44,6 +44,7 @@ import {
 	TimelineEventsResponse,
 	UnresolveReviewThreadResponse,
 	UpdateIssueResponse,
+	UpdatePullRequestBranchResponse,
 } from './graphql';
 import {
 	AccountType,
@@ -1201,11 +1202,55 @@ export class PullRequestModel extends IssueModel<PullRequest> implements IPullRe
 	}
 
 	async updateBranch(model: ConflictResolutionModel): Promise<boolean> {
-		if (this.item.mergeable === PullRequestMergeability.Conflict && (!model.resolvedConflicts || model.resolvedConflicts.size === 0)) {
+		if (!model.resolvedConflicts || model.resolvedConflicts.size === 0) {
 			throw new Error('Pull Request has conflicts but no resolutions were provided.');
 		}
-
 		Logger.debug(`Updating branch ${model.prHeadBranchName} to ${model.prBaseBranchName} - enter`, GitHubRepository.ID);
+		// For Conflict state, use the REST API approach with conflict resolution.
+		// For Unknown or NotMergeable states, the REST API approach will also be used as a fallback,
+		// though these states may fail for other reasons (e.g., blocked by branch protection).
+		return this.updateBranchWithConflictResolution(model!);
+	}
+
+	/**
+	 * Update the branch using the GitHub GraphQL API's UpdatePullRequestBranch mutation.
+	 * This is used when there are no conflicts between the head and base branches.
+	 */
+	public async updateBranchWithGraphQL(): Promise<boolean> {
+		Logger.debug(`Updating branch using GraphQL UpdatePullRequestBranch mutation - enter`, GitHubRepository.ID);
+
+		if (!this.head?.sha) {
+			Logger.error(`Cannot update branch: head SHA is not available`, GitHubRepository.ID);
+			return false;
+		}
+
+		try {
+			const { mutate, schema } = await this.githubRepository.ensure();
+
+			await mutate<UpdatePullRequestBranchResponse>({
+				mutation: schema.UpdatePullRequestBranch,
+				variables: {
+					input: {
+						pullRequestId: this.graphNodeId,
+						expectedHeadOid: this.head.sha
+					}
+				}
+			});
+
+			Logger.debug(`Updating branch using GraphQL UpdatePullRequestBranch mutation - done`, GitHubRepository.ID);
+			return true;
+		} catch (e) {
+			Logger.error(`Updating branch using GraphQL UpdatePullRequestBranch mutation failed: ${e}`, GitHubRepository.ID);
+			return false;
+		}
+	}
+
+	/**
+	 * Update the branch with conflict resolution using the REST API.
+	 * This is used when there are conflicts between the head and base branches.
+	 */
+	private async updateBranchWithConflictResolution(model: ConflictResolutionModel): Promise<boolean> {
+		Logger.debug(`Updating branch ${model.prHeadBranchName} with conflict resolution - enter`, GitHubRepository.ID);
 		try {
 			const { octokit } = await this.githubRepository.ensure();
 
@@ -1225,10 +1270,10 @@ export class PullRequestModel extends IssueModel<PullRequest> implements IPullRe
 			await octokit.call(octokit.api.git.updateRef, { owner: model.prHeadOwner, repo: model.repositoryName, ref: `heads/${model.prHeadBranchName}`, sha: newCommitSha });
 
 		} catch (e) {
-			Logger.error(`Updating branch ${model.prHeadBranchName} to ${model.prBaseBranchName} failed: ${e}`, GitHubRepository.ID);
+			Logger.error(`Updating branch ${model.prHeadBranchName} with conflict resolution failed: ${e}`, GitHubRepository.ID);
 			return false;
 		}
-		Logger.debug(`Updating branch ${model.prHeadBranchName} to ${model.prBaseBranchName} - done`, GitHubRepository.ID);
+		Logger.debug(`Updating branch ${model.prHeadBranchName} with conflict resolution - done`, GitHubRepository.ID);
 		return true;
 	}
 

src/github/pullRequestOverview.ts

@@ -17,6 +17,7 @@ import {
 	ITeam,
 	MergeMethod,
 	MergeMethodsAvailability,
+	PullRequestMergeability,
 	ReviewEventEnum,
 	ReviewState,
 } from './interface';
@@ -220,7 +221,13 @@ export class PullRequestOverviewPanel extends IssueOverviewPanel<PullRequestMode
 	}
 
 	private isUpdateBranchWithGitHubEnabled(): boolean {
-		return this._item.isActive || vscode.workspace.getConfiguration(PR_SETTINGS_NAMESPACE).get('experimentalUpdateBranchWithGitHub', false);
+		// With the GraphQL UpdatePullRequestBranch API, we can update branches even when not checked out
+		// (as long as there are no conflicts). If there are conflicts, we need the branch to be checked out.
+		const hasConflicts = this._item.item.mergeable === PullRequestMergeability.Conflict;
+		if (hasConflicts) {
+			return this._item.isActive;
+		}
+		return true;
 	}
 
 	protected override continueOnGitHub() {

src/github/pullRequestReviewCommon.ts

@@ -162,13 +162,16 @@ export namespace PullRequestReviewCommon {
 		refreshAfterUpdate: () => Promise<void>,
 		checkUpdateEnabled?: () => boolean
 	): Promise<void> {
-		if (checkUpdateEnabled && !checkUpdateEnabled()) {
-			await vscode.window.showErrorMessage(vscode.l10n.t('The pull request branch must be checked out to be updated.'), { modal: true });
+		// When there are conflicts and the PR is not checked out, we need local checkout to resolve them
+		const hasConflicts = ctx.item.item.mergeable === PullRequestMergeability.Conflict;
+		if (hasConflicts && checkUpdateEnabled && !checkUpdateEnabled()) {
+			await vscode.window.showErrorMessage(vscode.l10n.t('The pull request branch must be checked out to resolve conflicts.'), { modal: true });
 			return ctx.replyMessage(message, {});
 		}
 
-		if (ctx.folderRepositoryManager.repository.state.workingTreeChanges.length > 0 || ctx.folderRepositoryManager.repository.state.indexChanges.length > 0) {
-			await vscode.window.showErrorMessage(vscode.l10n.t('The pull request branch cannot be updated when the there changed files in the working tree or index. Stash or commit all change and then try again.'), { modal: true });
+		// Working tree/index checks only apply when the PR is checked out
+		if (ctx.item.isActive && (ctx.folderRepositoryManager.repository.state.workingTreeChanges.length > 0 || ctx.folderRepositoryManager.repository.state.indexChanges.length > 0)) {
+			await vscode.window.showErrorMessage(vscode.l10n.t('The pull request branch cannot be updated when there are changed files in the working tree or index. Stash or commit all change and then try again.'), { modal: true });
 			return ctx.replyMessage(message, {});
 		}
 		const mergeSucceeded = await ctx.folderRepositoryManager.tryMergeBaseIntoHead(ctx.item, true);

src/github/queries.gql

@@ -763,4 +763,13 @@ mutation ReplaceActorsForAssignable($input: ReplaceActorsForAssignableInput!) {
 			}
 		}
 	}
+}
+
+mutation UpdatePullRequestBranch($input: UpdatePullRequestBranchInput!) {
+	updatePullRequestBranch(input: $input) {
+		pullRequest {
+			id
+			headRefOid
+		}
+	}
 }

src/github/queriesExtra.gql

@@ -806,4 +806,13 @@ mutation EnqueuePullRequest($input: EnqueuePullRequestInput!) {
 			...MergeQueueEntryFragment
 		}
 	}
+}
+
+mutation UpdatePullRequestBranch($input: UpdatePullRequestBranchInput!) {
+	updatePullRequestBranch(input: $input) {
+		pullRequest {
+			id
+			headRefOid
+		}
+	}
 }