use default MSYS2 installation if update

Author: eine

README.md

@@ -6,21 +6,29 @@
   <a title="'action' workflow Status" href="https://github.com/eine/setup-msys2/actions"><img alt="'action' workflow Status" src="https://github.com/eine/setup-msys2/workflows/action/badge.svg"></a>
 </p>
 
-**setup-msys2** is a JavaScript GitHub Action (GHA) to setup a full-featured [MSYS2](https://www.msys2.org/) environment, using the GHA [toolkit](https://github.com/actions/toolkit).
+[MSYS2](https://www.msys2.org/) is available by default in [windows-latest](https://github.com/actions/virtual-environments/blob/master/images/win/Windows2019-Readme.md#msys2) virtual environment for GitHub Actions. However, the default installation is updated and it includes some pre-installed packages. Moreover, it is neither added to the PATH nor available as a custom `shell` option.
 
-The latest tarball available at [repo.msys2.org/distrib/x86_64](http://repo.msys2.org/distrib/x86_64/) is cached. Using the action extracts it and provides two entrypoints named `msys2` and `msys2do`.
+**setup-msys2** is a JavaScript GitHub Action (GHA) to optionally setup a stable [MSYS2](https://www.msys2.org/) environment in a temporal location, using the GHA [toolkit](https://github.com/actions/toolkit); and to provide two custom entrypoints.
+
+If option `update` is `true`, the default installation is used, in order to reduce startup latency. Otherwise, the latest tarball available at [repo.msys2.org/distrib/x86_64](http://repo.msys2.org/distrib/x86_64/) is downloaded and extracted.
 
 ## Usage
 
 ```yaml
   - uses: eine/setup-msys2@v0
+```
+
+Then, for multi-line scripts:
+
+```yaml
   - shell: msys2 {0}
     run: |
       uname -a
 ```
 
+Or, for single line commands:
+
 ```yaml
-  - uses: eine/setup-msys2@v0
   - run: msys2do uname -a
 ```
 

main.js

@@ -21,16 +21,22 @@ async function run() {
 
     await io.mkdirP(dest);
 
-    const distrib = await tc.downloadTool('https://github.com/msys2/msys2-installer/releases/download/2020-05-17/msys2-base-x86_64-20200517.tar.xz');
+    const update = core.getInput('update') == 'true';
 
-    await exec.exec('bash', ['-c', `7z x ${distrib.replace(/\\/g, '/')} -so | 7z x -aoa -si -ttar`], {cwd: dest} );
+    let drive = 'C:';
+
+    if (!update) {
+      drive = '%~dp0';
+      const distrib = await tc.downloadTool('https://github.com/msys2/msys2-installer/releases/download/2020-05-17/msys2-base-x86_64-20200517.tar.xz');
+      await exec.exec('bash', ['-c', `7z x ${distrib.replace(/\\/g, '/')} -so | 7z x -aoa -si -ttar`], {cwd: dest} );
+    }
 
     let cmd = path.join(dest, 'msys2do.cmd');
     fs.writeFileSync(cmd, [
       `setlocal`,
       `@echo off`,
       `IF NOT DEFINED MSYS2_PATH_TYPE set MSYS2_PATH_TYPE=` + core.getInput('path-type'),
-      `%~dp0\\msys64\\usr\\bin\\bash.exe --norc -ilceo pipefail "cd $OLDPWD && %*"`
+      drive + `\\msys64\\usr\\bin\\bash.exe --norc -ilceo pipefail "cd $OLDPWD && %*"`
     ].join('\r\n'));
 
     fs.writeFileSync(path.join(dest, 'msys2.cmd'), [
@@ -54,18 +60,19 @@ async function run() {
       core.startGroup(str);
     }
 
-    core.startGroup('Starting MSYS2 for the first time...');
-      if (core.getInput('update') == 'true') {
-        changeGroup('Updating packages...');
-        await pacman(['-Syuu']);
-        changeGroup('Killing remaining tasks...');
-        await exec.exec('taskkill', ['/F', '/FI', 'MODULES eq msys-2.0.dll']);
-        changeGroup('Final system upgrade...');
-        await pacman(['-Suu']);
-      } else {
-        await exec.exec('cmd', ['/D', '/S', '/C', cmd].concat(['uname', '-a']));
-      }
-    core.endGroup();
+    if (update) {
+      core.startGroup('Updating packages...');
+      await pacman(['-Syuu']);
+      changeGroup('Killing remaining tasks...');
+      await exec.exec('taskkill', ['/F', '/FI', 'MODULES eq msys-2.0.dll']);
+      changeGroup('Final system upgrade...');
+      await pacman(['-Suu']);
+      core.endGroup();
+    } else {
+      core.startGroup('Starting MSYS2 for the first time...');
+      await exec.exec('cmd', ['/D', '/S', '/C', cmd].concat(['uname', '-a']));
+      core.endGroup();
+    }
 
     let install = core.getInput('install');
     if (install != '' && install != 'false') {