support specifying global.json location with global-json-file input

README.md

@@ -51,6 +51,16 @@ steps:
     include-prerelease: true
 - run: dotnet build <my project>
 ```
+global.json in a subdirectory:
+```yml
+steps:
+- uses: actions/checkout@v2
+- uses: actions/setup-dotnet@v1
+  with:
+    global-json-file: csharp/global.json
+- run: dotnet build <my project>
+  working-directory: csharp
+```
 
 Matrix Testing:
 ```yaml

action.yml

@@ -7,6 +7,8 @@ branding:
 inputs:
   dotnet-version:
     description: 'Optional SDK version(s) to use. If not provided, will install global.json version when available. Examples: 2.2.104, 3.1, 3.1.x'
+  global-json-file:
+    description: 'Optional global.json location, if your global.json it''t located in the root of the repo.'
   source-url:
     description: 'Optional package source for which to set up authentication. Will consult any existing NuGet.config in the root of the repo and provide a temporary NuGet.config using the NUGET_AUTH_TOKEN environment variable as a ClearTextPassword'
   owner:

dist/index.js

@@ -9120,6 +9120,14 @@ function run() {
             // Proxy, auth, (etc) are still set up, even if no version is identified
             //
             let versions = core.getMultilineInput('dotnet-version');
+            const globalJsonFileInput = core.getInput('global-json-file');
+            if (globalJsonFileInput) {
+                const globalJsonPath = path.join(process.cwd(), globalJsonFileInput);
+                if (!fs.existsSync(globalJsonPath)) {
+                    throw new Error(`The specified global.json file '${globalJsonFileInput}' does not exist`);
+                }
+                versions.push(getVersionFromGlobalJson(globalJsonPath));
+            }
             if (!versions.length) {
                 // Try to fall back to global.json
                 core.debug('No version found, trying to find version from global.json');

src/setup-dotnet.ts

@@ -14,6 +14,18 @@ export async function run() {
     // Proxy, auth, (etc) are still set up, even if no version is identified
     //
     let versions = core.getMultilineInput('dotnet-version');
+
+    const globalJsonFileInput = core.getInput('global-json-file');
+    if (globalJsonFileInput) {
+      const globalJsonPath = path.join(process.cwd(), globalJsonFileInput);
+      if (!fs.existsSync(globalJsonPath)) {
+        throw new Error(
+          `The specified global.json file '${globalJsonFileInput}' does not exist`
+        );
+      }
+      versions.push(getVersionFromGlobalJson(globalJsonPath));
+    }
+
     if (!versions.length) {
       // Try to fall back to global.json
       core.debug('No version found, trying to find version from global.json');