Try to detect failed artifact downloads better

In one instance, the `git-sdk-64-minimal` artifact was downloaded
incompletely, but the Action thought it had worked and cached the
incomplete set of files.

Let's try harder to detect that situation and indicate a failed
download.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

src/downloader.ts

@@ -69,30 +69,33 @@ async function unzip(
   }
 
   return new Promise<void>((resolve, reject) => {
-    https.get(url, (res: Readable): void => {
-      res
-        .pipe(unzipper.Parse())
-        .on('entry', entry => {
-          if (!entry.path.startsWith(stripPrefix)) {
-            process.stderr.write(
-              `warning: skipping ${entry.path} because it does not start with ${stripPrefix}\n`
-            )
-          }
-          const entryPath = `${outputDirectory}/${entry.path.substring(
-            stripPrefix.length
-          )}`
-          progress(entryPath)
-          if (entryPath.endsWith('/')) {
-            mkdirp(entryPath.replace(/\/$/, ''))
-            entry.autodrain()
-          } else {
-            entry.pipe(fs.createWriteStream(`${entryPath}`))
-          }
-        })
-        .on('error', reject)
-        .on('finish', progress)
-        .on('finish', resolve)
-    })
+    https
+      .get(url, (res: Readable): void => {
+        res
+          .on('error', reject)
+          .pipe(unzipper.Parse())
+          .on('entry', entry => {
+            if (!entry.path.startsWith(stripPrefix)) {
+              process.stderr.write(
+                `warning: skipping ${entry.path} because it does not start with ${stripPrefix}\n`
+              )
+            }
+            const entryPath = `${outputDirectory}/${entry.path.substring(
+              stripPrefix.length
+            )}`
+            progress(entryPath)
+            if (entryPath.endsWith('/')) {
+              mkdirp(entryPath.replace(/\/$/, ''))
+              entry.autodrain()
+            } else {
+              entry.pipe(fs.createWriteStream(`${entryPath}`))
+            }
+          })
+          .on('error', reject)
+          .on('finish', progress)
+          .on('finish', resolve)
+      })
+      .on('error', reject)
   })
 }