Avoid slashes in the cacheId

We will use the `cacheId` as a file name of the `.zip` that we will
cache when writing to a non-empty output directory.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

__tests__/downloader.test.ts

@@ -56,5 +56,5 @@ test('can obtain build ID', async () => {
     undefined
   )
   expect(fetch).toHaveBeenCalledTimes(1)
-  expect(cacheId).toEqual('git-for-windows/git-22-git-sdk-64-minimal-71000')
+  expect(cacheId).toEqual('git-for-windows.git-22-git-sdk-64-minimal-71000')
 })

src/downloader.ts

@@ -187,6 +187,9 @@ export async function get(
     }
   }
 
-  const cacheId = `${repository}-${definitionId}-${artifactName}-${data.value[0].id}`
+  const cacheId = `${repository}-${definitionId}-${artifactName}-${data.value[0].id}`.replace(
+    '/',
+    '.'
+  )
   return {artifactName, stripPrefix, download, cacheId}
 }