Describe errors in System.run

src/model/system.js

@@ -48,11 +48,11 @@ class System {
       const exitCode = await exec(command, arguments_, { silent: true, listeners, ...options });
       showOutput();
       if (exitCode !== 0) {
-        throwErrorShowing(error);
+        throwErrorShowing(`Command returned non-zero exit code.\nError: ${error}`);
       }
     } catch (inCommandError) {
       showOutput();
-      throwErrorShowing(inCommandError);
+      throwErrorShowing(`In-command error caught: ${inCommandError}`);
     }
 
     return result;

src/model/versioning.js

@@ -148,7 +148,7 @@ export default class Versioning {
     try {
       await this.git(['fetch', '--unshallow']);
     } catch (error) {
-      core.warning(error);
+      core.warning(`Fetch --unshallow caught: ${error}`);
       await this.git(['fetch']);
     }
   }