Support updating PR branches

Author: jspahrsummers

src/github/README.md

@@ -252,6 +252,15 @@ MCP Server for the GitHub API, enabling file operations, repository management,
      - `pull_number` (number): Pull request number
    - Returns: Combined status check results and individual check details
 
+24. `update_pull_request_branch`
+   - Update a pull request branch with the latest changes from the base branch (equivalent to GitHub's "Update branch" button)
+   - Inputs:
+     - `owner` (string): Repository owner
+     - `repo` (string): Repository name
+     - `pull_number` (number): Pull request number
+     - `expected_head_sha` (optional string): The expected SHA of the pull request's HEAD ref
+   - Returns: Success message when branch is updated
+
 ## Search Query Syntax
 
 ### Code Search

src/github/index.ts

@@ -48,6 +48,7 @@ import {
   SearchCodeResponseSchema,
   SearchCodeSchema,
   SearchIssuesResponseSchema,
+  UpdatePullRequestBranchSchema,
   SearchIssuesSchema,
   SearchRepositoriesSchema,
   SearchUsersResponseSchema,
@@ -853,6 +854,31 @@ async function getPullRequestFiles(
   return z.array(PullRequestFileSchema).parse(await response.json());
 }
 
+async function updatePullRequestBranch(
+  owner: string,
+  repo: string,
+  pullNumber: number,
+  expectedHeadSha?: string
+): Promise<void> {
+  const response = await fetch(
+    `https://api.github.com/repos/${owner}/${repo}/pulls/${pullNumber}/update-branch`,
+    {
+      method: "PUT",
+      headers: {
+        Authorization: `token ${GITHUB_PERSONAL_ACCESS_TOKEN}`,
+        Accept: "application/vnd.github.v3+json",
+        "User-Agent": "github-mcp-server",
+        "Content-Type": "application/json",
+      },
+      body: expectedHeadSha ? JSON.stringify({ expected_head_sha: expectedHeadSha }) : undefined,
+    }
+  );
+
+  if (!response.ok) {
+    throw new Error(`GitHub API error: ${response.statusText}`);
+  }
+}
+
 async function getPullRequestStatus(
   owner: string,
   repo: string,
@@ -1017,6 +1043,11 @@ server.setRequestHandler(ListToolsRequestSchema, async () => {
         name: "get_pull_request_status",
         description: "Get the combined status of all status checks for a pull request",
         inputSchema: zodToJsonSchema(GetPullRequestStatusSchema)
+      },
+      {
+        name: "update_pull_request_branch",
+        description: "Update a pull request branch with the latest changes from the base branch",
+        inputSchema: zodToJsonSchema(UpdatePullRequestBranchSchema)
       }
     ],
   };
@@ -1261,6 +1292,12 @@ server.setRequestHandler(CallToolRequestSchema, async (request) => {
         return { content: [{ type: "text", text: JSON.stringify(status, null, 2) }] };
       }
 
+      case "update_pull_request_branch": {
+        const args = UpdatePullRequestBranchSchema.parse(request.params.arguments);
+        await updatePullRequestBranch(args.owner, args.repo, args.pull_number, args.expected_head_sha);
+        return { content: [{ type: "text", text: "Pull request branch updated successfully" }] };
+      }
+
       default:
         throw new Error(`Unknown tool: ${request.params.name}`);
     }

src/github/schemas.ts

@@ -812,4 +812,13 @@ export type GetPullRequestFiles = z.infer<typeof GetPullRequestFilesSchema>;
 export type PullRequestFile = z.infer<typeof PullRequestFileSchema>;
 export type GetPullRequestStatus = z.infer<typeof GetPullRequestStatusSchema>;
 export type StatusCheck = z.infer<typeof StatusCheckSchema>;
+// Schema for updating a pull request branch
+export const UpdatePullRequestBranchSchema = z.object({
+  owner: z.string().describe("Repository owner (username or organization)"),
+  repo: z.string().describe("Repository name"),
+  pull_number: z.number().describe("Pull request number"),
+  expected_head_sha: z.string().optional().describe("The expected SHA of the pull request's HEAD ref")
+});
+
 export type CombinedStatus = z.infer<typeof CombinedStatusSchema>;
+export type UpdatePullRequestBranch = z.infer<typeof UpdatePullRequestBranchSchema>;