Be more restrictive when fetching default branch #9

	name: Build Docker Build Env

	on:
	push:
	# Builds should happen on feature branches
	# Only successfully tested builds should be merged to main
	# We don't want to rebuild after testing and verifying
	branches-ignore:
	- 'main'
	paths:
	- '.github/workflows/buildDockerBuildEnv.yml'
	- 'dockerBuildEnv/*'
	workflow_dispatch:

	jobs:
	dockerBuild:
	runs-on: ubuntu-latest
	strategy:
	fail-fast: false
	matrix:
	platform:
	- 'arch'
	- 'clang'
	- 'gcc'
	env:
	defaultBranch: ${{ github.event.repository.default_branch }}

	steps:
	- uses: actions/checkout@v4

	- name: Fetch default branch
	run: \|
	git remote set-branches --add origin "${defaultBranch}"
	git fetch --depth 1 origin "${defaultBranch}"

	- name: Check for changes
	id: diff
	run: \|
	set +e
	git diff --exit-code --no-patch "origin/${defaultBranch}" dockerBuildEnv/makefile dockerBuildEnv/nas2d-${{ matrix.platform }}.* ; echo "modified=$?" >> $GITHUB_OUTPUT

	- name: Docker build
	if: ${{ fromJSON(steps.diff.outputs.modified) }}
	run: echo make build-image-${{ matrix.platform }}

	# - name: Docker login
	# if: ${{ fromJSON(steps.diff.outputs.modified) }}
	# run: echo "${{ secrets.GITHUB_TOKEN }}" \| docker login ghcr.io --username "${{ github.repository_owner }}" --password-stdin

	# - name: Docker push
	# if: ${{ fromJSON(steps.diff.outputs.modified) }}
	# run: make push-image-${{ matrix.platform }}

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