Feature Request: Restrict source branches in Repository Rulesets (e.g., only allow 'develop' to merge into 'main')

[SW-Wanted]

🏷️ Discussion Type

Product Feedback

Body

The Problem

When managing an organization repository with multiple collaborators, we often enforce strict Git workflows, such as:
other-branches ➔ Normal Merge ➔ develop ➔ Squash Merge ➔ main

To enforce this, we configure a Repository Ruleset targeting the main branch, enabling Require a pull request before merging and restricting the allowed merge methods strictly to Allow squash merging.

However, there is a security loophole: GitHub currently does not provide a native option within Rulesets to restrict the source branch of a Pull Request. This means that while direct commits to main are blocked, any user can still accidentally or intentionally open a Pull Request from a random feature-branch straight into main and bypass the develop branch entirely.

The Proposed Solution

It would be incredibly helpful if GitHub added a new rule inside the Repository Rulesets configuration (specifically under the Require a pull request before merging section or as a standalone branch rule) to restrict or whitelist allowed source branches.

Ideally, when setting up a rule for a target branch (e.g., main), we should be able to configure:

• Allowed Source Branches: A field where we can specify branch names or patterns (e.g., develop) that are permitted to target this branch in a Pull Request. All other source branches would be blocked automatically by the platform UI.

Current Workaround

Right now, the only way to achieve this behavior is by writing custom GitHub Actions workflows to validate the github.head_ref and enforcing them via Require status checks to pass. Having this natively built into Repository Rulesets would make organization management much cleaner, more secure, and easier to scale.

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[BradPerbs]

+1 for native support. For anyone who needs the workaround today, there are two details that make it airtight:

name: pr-source-guard
on:
  pull_request:
    branches: [main]
    types: [opened, reopened, synchronize, edited]   # 'edited' catches retargeting a PR to main
jobs:
  source-branch:
    runs-on: ubuntu-latest
    steps:
      - if: github.head_ref != 'develop' || github.event.pull_request.head.repo.full_name != github.repository
        env:
          HEAD: ${{ github.event.pull_request.head.repo.full_name }}:${{ github.head_ref }}
        run: |
          echo "::error::PRs into main must come from develop in this repo (got $HEAD)"
          exit 1

Checking head.repo stops a fork's branch that happens to be named develop from passing. Passing the branch name through env avoids script injection. In the main ruleset, require source-branch and set its source to GitHub Actions so no other app can report that check.

[kurupdevs]

+1 for native support too. Two additions for anyone rolling this out at org scale:

1. Don't copy the guard workflow into every repo. On Team and Enterprise plans you can enforce it once with an organization-level ruleset targeting main (org Settings → Rules → Rulesets) requiring the source-branch status check, combined with a required workflow so the check itself is injected into every repo's PRs automatically. That way you maintain one file instead of N.

2. Watch the bypass list. Anyone on the ruleset's bypass list (usually admins) can still merge a PR from the wrong source branch even when the check fails, because bypass applies to the whole ruleset. Keep that list as small as possible, and periodically audit who has it — otherwise the guard only constrains non-admin contributors.

The workflow approach remains the best available today; these two points just close the gaps that tend to appear once you scale it past a single repo.