Clear git-promise timeout when git command was successful

[campersau]

While trying to migrate from grunt to script files, I noticed that the mocha unittest weren't existing right away. I tracked the problem down with wtfnode to our git-promise timeout (introduced in #1192) which wasn't cancelled if the git call was successful and didn't timed out.

[ylecuyer]

Nice finding. Maybe we can add a test for it? Just checking that clearTimeout is called wdyt?

[campersau]

I could add a test like this but hacking global variables for that feels a bit dirty and may have sideeffets when other code also uses it.

const expect = require('expect.js');
const git = require('../source/git-promise');

describe('git-promise', () => {
    it('should clear git timeout when successful', async () => {
        let clearTimeoutCallCount = 0;
        const originalClearTimeout = clearTimeout;
        clearTimeout = (arg) => {
            clearTimeoutCallCount++;
            originalClearTimeout(arg);
        }

        try {
            await git(['version']);

            expect(clearTimeoutCallCount).to.equal(1);
        } finally {
            clearTimeout = originalClearTimeout;
        }
    });
});