add set-output command

packages/core/__tests__/lib.test.ts

@@ -114,6 +114,11 @@ describe('@actions/core', () => {
     expect(core.getInput('special chars_\'\t"\\')).toBe('\'\t"\\ repsonse')
   })
 
+  it('setOutput produces the correct command', () => {
+    core.setOutput('some output', 'some value')
+    assertWriteCalls([`##[set-output name=some output;]some value${os.EOL}`])
+  })
+
   it('setNeutral sets the correct exit code', () => {
     core.setFailed('Failure message')
     expect(process.exitCode).toBe(ExitCode.Failure)

packages/core/src/core.ts

@@ -61,6 +61,16 @@ export function getInput(name: string, options?: InputOptions): string {
   return val.trim()
 }
 
+/**
+ * Sets the value of an output.
+ *
+ * @param     name     name of the output to set
+ * @param     value    value to store
+ */
+export function setOutput(name: string, value: string): void {
+  issueCommand('set-output', {'name': name}, value)
+}
+
 //-----------------------------------------------------------------------
 // Results
 //-----------------------------------------------------------------------