Wrap konfig load from scripts tests to avoid changing CWD (#4067)

* chore: add utility method to get konfig from scripts tests

Local scripts specs should be be caught by the changing current
directory when loading `konfig.coffee` (which loads `cwd.coffee`,
which changes the cwd to `packages/server`). This was throwing
snapshot tests into saving into a wrong folder until I have noticed
this and fixed in
[v8.0.3](https://github.com/bahmutov/snap-shot-core/releases/tag/v8.0.3)

* linting

* add more comments

scripts/unit/konfig-spec.js

@@ -0,0 +1,45 @@
+const la = require('lazy-ass')
+const is = require('check-more-types')
+const { join } = require('path')
+
+/* eslint-env mocha */
+describe('konfig check', () => {
+  /*
+    script tests should NOT suddenly change the current working directory to
+    packages/server - otherwise the local path filenames might be all wrong
+    and unexpected. The current working directory changes when we
+    require `packages/server/lib/konfig` which in tern requires
+    `lib/cwd` which changes CWD.
+
+    From the scripts unit tests we should not use `lib/konfig` directly,
+    instead we should use `binary/get-config` script to get the konfig function.
+  */
+
+  let cwd
+
+  before(() => {
+    cwd = process.cwd()
+    la(
+      !cwd.includes(join('packages', 'server')),
+      'process CWD is set to',
+      cwd,
+      'for some reason'
+    )
+    // if the above assertion breaks, it means some script in binary scripts
+    // loads "lib/konfig" directly, which unexpectedly changes the CWD.
+  })
+
+  it('does not change CWD on load', () => {
+    const konfig = require('../binary/get-config')()
+    const cwdAfter = process.cwd()
+
+    la(
+      cwd === cwdAfter,
+      'previous cwd',
+      cwd,
+      'differs after loading konfig',
+      cwdAfter
+    )
+    la(is.fn(konfig), 'expected konfig to be a function', konfig)
+  })
+})