refactor: port bash, batch files to javascript (electron#23)

* feat: add cli args to 'e fetch' and 'e bootstrap'

* refactor: minor --help message readability changes

* refactor: minor --help message readability changes

* fix: don't use `git rev-parse --show-toplevel`

When running in `git bash`, we want pathnames like "/c/Users/IEUser"
but `git rev-parse` returns "C:/Users/IEUser".

* refactor: move everything to portable JS scripts

The intent is to have uniform functionality between platforms
and to reduce the number of scripts that have to be maintained.

* chore: improve error messages and documentation

* chore: address some review comments

* chore: address some review comments

* feat: let user specify source and target in `e pr`

* fixup! feat: let user specify source and target in `e pr`

* chore: prettier

* refactor: don't specify e in try-catch if not used

* feat: add tests and coverage

* feat: add "npm run test" pull_request to workflows

.github/workflows/pull_request.yml

@@ -0,0 +1,20 @@
+name: Continous Integration
+
+on: pull_request
+
+jobs:
+  build:
+    name: Test pull requests
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+      with:
+        fetch-depth: 1
+    - name: Use Node.js v12.x
+      uses: actions/setup-node@v1
+      with:
+        node-version: 12.x
+    - name: npm install and test
+      run: |
+        npm install
+        npm test

.gitignore

@@ -1,8 +1,6 @@
+.nyc_output/
+configs
+coverage
 node_modules
-config.yml
-config.*.yml
-!config.example.yml
-third_party
 package-lock.json
-
-generated.env.*
+third_party

.prettierrc.json

@@ -0,0 +1,8 @@
+{
+  "trailingComma": "all",
+  "tabWidth": 2,
+  "singleQuote": true,
+  "printWidth": 100,
+  "parser": "typescript",
+  "endOfLine": "lf"
+}