fix: harden for option injection

[sparten11740]

Explicitly whitelist the flags that can be used with the commit and resetLastCommit function

Closes #37

[mbaraniak-exodus]

Reviewed. The implementation is way more secure than it was, but I would still recommend hardening.

[mbaraniak-exodus]

Unfortunately, this check in some corner cases will not be enough. There are multiple shell characters which will bypass this restriction. For example, run next command in bash:

git add ``-e
: !/bin/sh

git add ${}-e
: !/bin/sh

Our current implementation in not passing shell option to the nodeSpawnSync, leaving us safe.

const { stdout, stderr, status } = nodeSpawnSync(command, args, { encoding: 'utf8', ...options })

Nevertheless, if any client (or malicious actor via PP) will pass options with the shell=true, it would be easy to bypass startswith check

> node
const cp = require('child_process')
cp.spawnSync('git', ['add', '``-e'], { encoding: 'utf8', shell:false}) // not vulnerable
{
  status: 128,
  signal: null,
  output: [ null, '', "fatal: pathspec '``-e' did not match any files\n" ],
  pid: 38227,
  stdout: '',
  stderr: "fatal: pathspec '``-e' did not match any files\n"
}
> cp.spawnSync('git', ['add', '``-e'], { encoding: 'utf8', shell:true}) // vulnerable