diff --git a/dist/versions.js b/dist/versions.js
index c5a7ae6..f01d5ea 100644
--- a/dist/versions.js
+++ b/dist/versions.js
@@ -38,11 +38,10 @@ async function selectBranch(branch) {
     throw new Error(`Branch ${branch} not found`);
 }
 async function selectPr(pr) {
-    var _a;
     const versions = await git_1.lsRemote();
     if (pr in versions.pull) {
         const prheads = versions.pull[pr];
-        const sha = (_a = prheads.merge) !== null && _a !== void 0 ? _a : prheads.head;
+        const sha = prheads.head;
         if (sha) {
             return new VersionImpl(`#${pr}`, sha, 'pull', `pull request #${pr}`);
         }
diff --git a/dist/win-install.js b/dist/win-install.js
index fe1c8e0..ef85613 100644
--- a/dist/win-install.js
+++ b/dist/win-install.js
@@ -7,27 +7,30 @@ const toolCache = require("@actions/tool-cache");
 const os = require("os");
 const path = require("path");
 const semver = require("semver");
+function getInstallerUrl(version) {
+    const ver = version.version;
+    if (version.type === 'heads') {
+        // we only use appveyor ci artifacts for branch version
+        const arch = os.arch() === 'x64' ? 'x64' : 'x86';
+        return `https://ci.appveyor.com/api/projects/waruqi/xmake/artifacts/xmake-installer.exe?branch=${ver}&pr=false&job=Image%3A+Visual+Studio+2017%3B+Platform%3A+${arch}`;
+    }
+    else if (version.type === 'pull') {
+        throw new Error('PR builds for windows is not supported');
+    }
+    else {
+        // we cannot use appveyor ci artifacts, the old version links may be broken.
+        const arch = os.arch() === 'x64' ? 'win64' : 'win32';
+        return semver.gt(ver, '2.2.6')
+            ? `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.${arch}.exe`
+            : `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.exe`;
+    }
+}
 async function winInstall(version) {
     const ver = version.version;
     let toolDir = toolCache.find('xmake', ver);
     if (!toolDir) {
         const installer = await core.group(`download xmake ${version}`, async () => {
-            let url = '';
-            if (version.type === 'heads') {
-                // we only use appveyor ci artifacts for branch version
-                const arch = os.arch() === 'x64' ? 'x64' : 'x86';
-                url = `https://ci.appveyor.com/api/projects/waruqi/xmake/artifacts/xmake-installer.exe?branch=${ver}&pr=false&job=Image%3A+Visual+Studio+2017%3B+Platform%3A+${arch}`;
-            }
-            else if (version.type === 'pull') {
-                throw new Error('PR builds for windows is not supported');
-            }
-            else {
-                // we cannot use appveyor ci artifacts, the old version links may be broken.
-                const arch = os.arch() === 'x64' ? 'win64' : 'win32';
-                url = semver.gt(ver, '2.2.6')
-                    ? `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.${arch}.exe`
-                    : `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.exe`;
-            }
+            const url = getInstallerUrl(version);
             core.info(`downloading from ${url}`);
             const file = await toolCache.downloadTool(url);
             const exe = path.format({ ...path.parse(file), ext: '.exe', base: undefined });
diff --git a/src/git.ts b/src/git.ts
index c058651..3571c64 100644
--- a/src/git.ts
+++ b/src/git.ts
@@ -8,9 +8,22 @@ function makeOpt(ref: string): { cwd: string } {
 }
 
 export type RefDic = {
+    /** branches */
     heads: Record<string, string>;
+    /** tags */
     tags: Record<string, string>;
-    pull: Record<number, { head?: string; merge?: string }>;
+    /** pull requests */
+    pull: Record<
+        number,
+        {
+            /** the current state of the pull request */
+            head: string;
+            /** the current branch we're merging onto */
+            base?: string;
+            /** merge result */
+            merge?: string;
+        }
+    >;
 };
 
 export async function lsRemote(): Promise<RefDic> {
diff --git a/src/versions.ts b/src/versions.ts
index db69ec6..e315560 100644
--- a/src/versions.ts
+++ b/src/versions.ts
@@ -30,7 +30,7 @@ async function selectPr(pr: number): Promise<Version> {
     const versions = await lsRemote();
     if (pr in versions.pull) {
         const prheads = versions.pull[pr];
-        const sha = prheads.merge ?? prheads.head;
+        const sha = prheads.head;
         if (sha) {
             return new VersionImpl(`#${pr}`, sha, 'pull', `pull request #${pr}`);
         }
diff --git a/src/win-install.ts b/src/win-install.ts
index 2507db0..ee45fa6 100644
--- a/src/win-install.ts
+++ b/src/win-install.ts
@@ -7,25 +7,29 @@ import * as path from 'path';
 import * as semver from 'semver';
 import { Version } from './versions';
 
+function getInstallerUrl(version: Version): string {
+    const ver = version.version;
+    if (version.type === 'heads') {
+        // we only use appveyor ci artifacts for branch version
+        const arch = os.arch() === 'x64' ? 'x64' : 'x86';
+        return `https://ci.appveyor.com/api/projects/waruqi/xmake/artifacts/xmake-installer.exe?branch=${ver}&pr=false&job=Image%3A+Visual+Studio+2017%3B+Platform%3A+${arch}`;
+    } else if (version.type === 'pull') {
+        throw new Error('PR builds for windows is not supported');
+    } else {
+        // we cannot use appveyor ci artifacts, the old version links may be broken.
+        const arch = os.arch() === 'x64' ? 'win64' : 'win32';
+        return semver.gt(ver, '2.2.6')
+            ? `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.${arch}.exe`
+            : `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.exe`;
+    }
+}
+
 export async function winInstall(version: Version): Promise<void> {
     const ver = version.version;
     let toolDir = toolCache.find('xmake', ver);
     if (!toolDir) {
         const installer = await core.group(`download xmake ${version}`, async () => {
-            let url = '';
-            if (version.type === 'heads') {
-                // we only use appveyor ci artifacts for branch version
-                const arch = os.arch() === 'x64' ? 'x64' : 'x86';
-                url = `https://ci.appveyor.com/api/projects/waruqi/xmake/artifacts/xmake-installer.exe?branch=${ver}&pr=false&job=Image%3A+Visual+Studio+2017%3B+Platform%3A+${arch}`;
-            } else if (version.type === 'pull') {
-                throw new Error('PR builds for windows is not supported');
-            } else {
-                // we cannot use appveyor ci artifacts, the old version links may be broken.
-                const arch = os.arch() === 'x64' ? 'win64' : 'win32';
-                url = semver.gt(ver, '2.2.6')
-                    ? `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.${arch}.exe`
-                    : `https://github.com/xmake-io/xmake/releases/download/${ver}/xmake-${ver}.exe`;
-            }
+            const url = getInstallerUrl(version);
             core.info(`downloading from ${url}`);
             const file = await toolCache.downloadTool(url);
             const exe = path.format({ ...path.parse(file), ext: '.exe', base: undefined });