## **Description**

Our CI was setup to compare each branch with `develop`, and run any
tests that have changed since `develop` extra times to catch new flaky
test regressions. Unfortunately this was happening even for PRs that do
not target develop, resulting in massive lists of "changed" tests that
ended up causing persistent test timeouts.

The quality gate should only impact PRs that target `develop`. PRs that
target other branches no longer repeat "changed" tests. This should fix
release PR e2e test timeouts caused by excessive e2e test runs.

You can see an example of this problem occurring here:
https://app.circleci.com/pipelines/github/MetaMask/metamask-extension/98357/workflows/b61a16b5-acfd-411f-b82e-7a31706ca658/jobs/3660843
Notice that
`/home/circleci/project/test/e2e/tests/request-queuing/ui.spec.js`
appears 6 times in the full test list, as to every other "changed" test.

[![Open in GitHub
Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/MetaMask/metamask-extension/pull/26846?quickstart=1)

## **Related issues**

This quality gate was first introduced in #24556

## **Manual testing steps**

The script can be run locally if you setup "fake" CircleCI environment
variables to allow it to run properly. For example:

```
CIRCLE_PULL_REQUEST=#26822 yarn tsx ./.circleci/scripts/git-diff-develop.ts
```


The CI run for this PR can be viewed as well:
https://app.circleci.com/pipelines/github/MetaMask/metamask-extension/98369/workflows/e9de2170-a19e-433e-a83c-846eeb239842/jobs/3661034

## **Screenshots/Recordings**

N/A

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I’ve included tests if applicable
- [x] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/develop/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.