Add 'latest' version alias (#42)

Allow a user to specify the cmake-version as `latest` instead of an
empty string to help clarity in workflow files.

.github/workflows/latest.yml

@@ -0,0 +1,27 @@
+on:
+  pull_request:
+    branches: [master]
+
+jobs:
+  latest_version:
+    runs-on: ${{ matrix.os }}
+    name: Test latest version
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v1
+
+    - name: Setup cmake
+      uses: ./
+      id: setup
+      with:
+        cmake-version: 'latest'
+
+    - name: Run cmake --version
+      shell: bash
+      run: |
+        VERSION=`cmake --version`
+        echo $VERSION

README.md

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Setup cmake
-      uses: jwlawson/actions-setup-cmake@v1.9
+      uses: jwlawson/actions-setup-cmake@v1.10
       with:
         cmake-version: '3.16.x'
     - name: Use cmake
@@ -32,6 +32,9 @@ There are three options for the action:
   version `3.2.x`. By default it is empty which will give the latest CMake
   version available on GitHub.
 
+  The version can also be specified to be `latest` which is equivalent to
+  leaving it blank and will give the latest version.
+
   The [version tests] show some expected values for given versions.
 
 * `github-api-token` is optional, but is used to authenticate with GitHub's

package.json

@@ -1,6 +1,6 @@
 {
   "name": "actions-setup-cmake",
-  "version": "1.9.0",
+  "version": "1.10.0",
   "description": "GitHub action to setup cmake",
   "main": "dist/index.js",
   "repository": {

src/index.ts

@@ -4,7 +4,9 @@ import * as version from './version';
 
 async function run() {
   try {
-    const required_version = core.getInput('cmake-version');
+    const requested_version = core.getInput('cmake-version');
+    const required_version =
+      requested_version === 'latest' ? '' : requested_version;
     const api_token = core.getInput('github-api-token');
     const all_version_info = await version.getAllVersionInfo(api_token);
     const chosen_version_info = version.getLatestMatching(