Fix runProcess to fully finish the process (#41)

`exec` did not wait for the `git` process to finish, which caused issues
when using `git checkout` >1 time in a row. We should have been using
the `spawn` API instead.

src/utils.ts

@@ -1,6 +1,6 @@
 /* eslint-disable no-console */
 
-import { exec, ExecOptions } from "child_process";
+import { spawn, SpawnOptionsWithoutStdio } from "child_process";
 
 import { Point } from "@influxdata/influxdb-client";
 
@@ -22,19 +22,29 @@ const createCountPoint = (
 
 const runProcess = (
   cmd: string,
-  options?: ExecOptions
+  args: string[],
+  options?: SpawnOptionsWithoutStdio
 ): Promise<[string, string]> =>
   new Promise((resolve, reject) => {
-    exec(cmd, options, (error, stdout, stderr) => {
-      if (error) {
-        return reject(error);
-      }
-      if (stdout instanceof Buffer || stderr instanceof Buffer) {
-        return reject(
-          new Error("stdout or stderr is Buffer, which is not supported")
-        );
+    const child = spawn(cmd, args, options);
+
+    let output = "";
+    child.stdout.on("data", (data) => {
+      output += data;
+    });
+
+    let errorOutput = "";
+    child.stderr.on("data", (data) => {
+      errorOutput += data;
+    });
+
+    child.on("error", reject);
+    child.on("close", (code) => {
+      if (code === 0) {
+        resolve([output, errorOutput]);
+      } else {
+        reject(new Error(`Command exited with code ${code}: ${errorOutput}`));
       }
-      return resolve([stdout, stderr]);
     });
   });
 

tests/utils.test.ts

@@ -4,20 +4,23 @@ import { runProcess } from "../src/utils";
 
 test.describe("runProcess", () => {
   test("captures stdout", async () => {
-    const [stdout, stderr] = await runProcess("echo 'hello world'");
+    const [stdout, stderr] = await runProcess("echo", ["hello world"]);
     expect(stdout).toEqual("hello world\n");
     expect(stderr).toEqual("");
   });
 
   test("captures stderr", async () => {
-    const [stdout, stderr] = await runProcess("echo 'hello world' 1>&2");
+    const [stdout, stderr] = await runProcess("node", [
+      "-e",
+      "console.error('hello world')",
+    ]);
     expect(stdout).toEqual("");
     expect(stderr).toEqual("hello world\n");
   });
 
   test("errors on failures", async () => {
     try {
-      await runProcess("fake-process");
+      await runProcess("fake-process", []);
     } catch (error) {
       expect(error).toBeTruthy();
     }