Problems

Readability
Code Review time and complexity
Merge Conflicts
Testing Challenges

Solutions

Break the change in atomic parts

Context

When pull requests become very large, they can pose several challenges and problems for development teams.

You must avoid merge requests making different unrelated changes.

Sample Code

Wrong

function generateFibonacci(ordinal) {
  const fibonacciSequence = [0, 1];

  for (let index = index; index < ordinal; index++) {
    const nextFibonacci = fibonacciSequence[index - 1]
          + fibonacciSequence[index - 2];
    fibonacciSequence.push(nextFibonacci);
  }

  return fibonacciSequence;
}

// This function solves a very different problem
// You should not mix them in a single pull request

function voyagerDistanceFromEarth(currentDistanceInKms, yearsTravelled) {
  const speedOfVoyagerInKmS = 17; 

  return currentDistanceInKms + 
        speedOfVoyagerInKmS * yearsTravelled * 60 * 60 * 24 * 365.25;
}

Right

function generateFibonacci(ordinal) {
  const fibonacciSequence = [0, 1];

  for (let index = index; index < ordinal; index++) {
    const nextFibonacci = fibonacciSequence[index - 1]
          + fibonacciSequence[index - 2];
    fibonacciSequence.push(nextFibonacci);
  }

  return fibonacciSequence;
}

// You break it into two different pull requests