fix: add check to make sure that the head and the base are different (#…

…115)

Co-authored-by: Gregor Martynus <39992+gr2m@users.noreply.github.com>

src/compose-create-pull-request.ts

@@ -20,6 +20,11 @@ export async function composeCreatePullRequest(
     update = false,
   }: Options
 ) {
+  if (head === base) {
+    throw new Error(
+      '[octokit-plugin-create-pull-request] "head" cannot be the same value as "base"'
+    );
+  }
   const changes = Array.isArray(changesOption)
     ? changesOption
     : [changesOption];

test/base-head-same-value.test.ts

@@ -0,0 +1,31 @@
+import { Octokit as Core } from "@octokit/core";
+import { createPullRequest } from "../src";
+
+const Octokit = Core.plugin(createPullRequest);
+
+test("Base and Head equality", async () => {
+  const octokit = new Octokit();
+
+  try {
+    await octokit.createPullRequest({
+      owner: "gr2m",
+      repo: "pull-request-test",
+      title: "One comes, one goes",
+      body: "because",
+      base: "patch",
+      head: "patch",
+      changes: {
+        files: {
+          "path/to/file1.txt": "Content for file1",
+          "path/to/file2.txt": "Content for file2",
+        },
+        commit: "why",
+      },
+    });
+    throw new Error("Should not resolve");
+  } catch (error) {
+    expect((error as Error).message).toEqual(
+      '[octokit-plugin-create-pull-request] "head" cannot be the same value as "base"'
+    );
+  }
+});