Add base branch editing functionality

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

Author: Copilot

src/github/pullRequestModel.ts

@@ -1199,6 +1199,37 @@ export class PullRequestModel extends IssueModel<PullRequest> implements IPullRe
 		return true;
 	}
 
+	/**
+	 * Update the base branch of the pull request.
+	 * @param newBaseBranch The new base branch name
+	 */
+	async updateBaseBranch(newBaseBranch: string): Promise<void> {
+		Logger.debug(`Updating base branch to ${newBaseBranch} - enter`, PullRequestModel.ID);
+		try {
+			const { mutate, schema } = await this.githubRepository.ensure();
+
+			const { data } = await mutate({
+				mutation: schema.UpdatePullRequest,
+				variables: {
+					input: {
+						pullRequestId: this.graphNodeId,
+						baseRefName: newBaseBranch,
+					},
+				},
+			});
+
+			if (data?.updateIssue?.issue) {
+				// Update the local base branch reference
+				this.base.name = newBaseBranch;
+				this._onDidChange.fire({ base: true });
+			}
+			Logger.debug(`Updating base branch to ${newBaseBranch} - done`, PullRequestModel.ID);
+		} catch (e) {
+			Logger.error(`Updating base branch to ${newBaseBranch} failed: ${e}`, PullRequestModel.ID);
+			throw e;
+		}
+	}
+
 	/**
 	 * Get existing requests to review.
 	 */

src/github/pullRequestOverview.ts

@@ -425,6 +425,8 @@ export class PullRequestOverviewPanel extends IssueOverviewPanel<PullRequestMode
 				return this.openCommitChanges(message);
 			case 'pr.delete-review':
 				return this.deleteReview(message);
+			case 'pr.change-base-branch':
+				return this.changeBaseBranch(message);
 		}
 	}
 
@@ -805,6 +807,59 @@ export class PullRequestOverviewPanel extends IssueOverviewPanel<PullRequestMode
 		}
 	}
 
+	private async changeBaseBranch(message: IRequestMessage<void>): Promise<void> {
+		const quickPick = vscode.window.createQuickPick<vscode.QuickPickItem & { branch?: string }>();
+
+		try {
+			quickPick.busy = true;
+			quickPick.canSelectMany = false;
+			quickPick.placeholder = 'Select a new base branch';
+			quickPick.show();
+
+			// List branches from the repository
+			const branches = await this._item.githubRepository.listBranches(
+				this._item.remote.owner,
+				this._item.remote.repositoryName
+			);
+
+			quickPick.items = branches
+				.filter(branch => branch !== this._item.base.name)
+				.map(branch => ({
+					label: branch,
+					branch: branch
+				}));
+
+			quickPick.busy = false;
+			const acceptPromise = asPromise<void>(quickPick.onDidAccept).then(() => {
+				return quickPick.selectedItems[0]?.branch;
+			});
+			const hidePromise = asPromise<void>(quickPick.onDidHide);
+			const selectedBranch = await Promise.race<string | void>([acceptPromise, hidePromise]);
+			quickPick.busy = true;
+			quickPick.enabled = false;
+
+			if (selectedBranch) {
+				try {
+					// Update the base branch using GraphQL mutation
+					await this._item.updateBaseBranch(selectedBranch);
+					// Refresh the panel to reflect the changes
+					await this.refreshPanel();
+					await this._replyMessage(message, {});
+				} catch (e) {
+					Logger.error(formatError(e), PullRequestOverviewPanel.ID);
+					vscode.window.showErrorMessage(vscode.l10n.t('Changing base branch failed. {0}', formatError(e)));
+					this._throwError(message, `${formatError(e)}`);
+				}
+			}
+		} catch (e) {
+			Logger.error(formatError(e), PullRequestOverviewPanel.ID);
+			vscode.window.showErrorMessage(formatError(e));
+		} finally {
+			quickPick.hide();
+			quickPick.dispose();
+		}
+	}
+
 	override dispose() {
 		super.dispose();
 		disposeAll(this._prListeners);

webviews/common/context.tsx

@@ -92,6 +92,7 @@ export class PRContext {
 	public readyForReviewAndMerge = (args: { mergeMethod: MergeMethod }): Promise<ReadyForReview> => this.postMessage({ command: 'pr.readyForReviewAndMerge', args });
 
 	public addReviewers = () => this.postMessage({ command: 'pr.change-reviewers' });
+	public changeBaseBranch = () => this.postMessage({ command: 'pr.change-base-branch' });
 	public changeProjects = (): Promise<ProjectItemsReply> => this.postMessage({ command: 'pr.change-projects' });
 	public removeProject = (project: IProjectItem) => this.postMessage({ command: 'pr.remove-project', args: project });
 	public addMilestone = () => this.postMessage({ command: 'pr.add-milestone' });

webviews/components/header.tsx

@@ -52,7 +52,7 @@ export function Header({
 				owner={owner}
 				repo={repo}
 			/>
-			<Subtitle state={state} stateReason={stateReason} head={head} base={base} author={author} isIssue={isIssue} isDraft={isDraft} codingAgentEvent={codingAgentEvent} />
+			<Subtitle state={state} stateReason={stateReason} head={head} base={base} author={author} isIssue={isIssue} isDraft={isDraft} codingAgentEvent={codingAgentEvent} canEdit={canEdit} />
 			<div className="header-actions">
 				<ButtonGroup
 					isCurrentlyCheckedOut={isCurrentlyCheckedOut}
@@ -248,9 +248,11 @@ interface SubtitleProps {
 	base: string;
 	head: string;
 	codingAgentEvent: TimelineEvent | undefined;
+	canEdit: boolean;
 }
 
-function Subtitle({ state, stateReason, isDraft, isIssue, author, base, head, codingAgentEvent }: SubtitleProps): JSX.Element {
+function Subtitle({ state, stateReason, isDraft, isIssue, author, base, head, codingAgentEvent, canEdit }: SubtitleProps): JSX.Element {
+	const { changeBaseBranch } = useContext(PullRequestContext);
 	const { text, color, icon } = getStatus(state, !!isDraft, isIssue, stateReason);
 	const copilotStatus = copilotEventToStatus(codingAgentEvent);
 	let copilotStatusIcon: JSX.Element | undefined;
@@ -273,7 +275,13 @@ function Subtitle({ state, stateReason, isDraft, isIssue, author, base, head, co
 				<div className="merge-branches">
 					<AuthorLink for={author} /> {!isIssue ? (<>
 						{getActionText(state)} into{' '}
-						<code className="branch-tag">{base}</code> from <code className="branch-tag">{head}</code>
+						<code className="branch-tag">{base}</code>
+						{canEdit && state === GithubItemStateEnum.Open ? (
+							<button title="Change base branch" onClick={changeBaseBranch} className="icon-button">
+								{editIcon}
+							</button>
+						) : null}
+						{' '}from <code className="branch-tag">{head}</code>
 					</>) : null}
 				</div>
 			</div>