feat: switch default container image from Ubuntu to Alpine

[patrickhoefler]

No description provided.

[Copilot]

Pull Request Overview

This PR switches the default container image from Ubuntu to Alpine while still providing support for an Ubuntu-based image.

• Dockerfile now builds an Alpine-based release image
• A dedicated Dockerfile.ubuntu is created while Dockerfile.alpine is removed
• README.md, Makefile, .goreleaser.yaml, and workflow files are updated to reflect these changes

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/cmd/testdata/Dockerfile.golden.dot	Adjusted coordinate values in the graph to match new expectations
README.md	Updated image tags and commands to clarify which image is default and which is Ubuntu-based
Makefile	Revised build targets to reference the updated Dockerfiles for Alpine and Ubuntu
Dockerfile.ubuntu	New file for building the Ubuntu-based image
Dockerfile.alpine	Removed in favor of the unified Dockerfile for Alpine
Dockerfile	Modified to use Alpine as the base image instead of Ubuntu
.goreleaser.yaml	Updated image templates to include both Alpine (default) and Ubuntu tags
.github/workflows/lint_and_test.yml	Updated workflow commands to test the Ubuntu-based image in particular scenarios

[Copilot]

Pull Request Overview

This PR changes the default container image from Ubuntu to Alpine, introduces a dedicated Ubuntu variant, and updates associated build/test tooling.

• Default Dockerfile is now Alpine-based and a new Dockerfile.ubuntu provides an Ubuntu-based image.
• Build scripts and CI workflows are updated to reflect the new default and to explicitly build/test the Ubuntu variant.
• Documentation and release configuration (README.md, .goreleaser.yaml) are adjusted to mark Alpine as default and add Ubuntu tags.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/cmd/testdata/Dockerfile.golden.dot	Tweaked graph coordinates to match the new default (Alpine) image
README.md	Marked Alpine image as default and updated Docker run tags for both Alpine and Ubuntu
Makefile	Swapped Dockerfile references for Alpine/Ubuntu targets and enabled CGO_ENABLED=0 for Linux
Dockerfile	Switched base to Alpine, updated package manager commands
Dockerfile.ubuntu	Added Ubuntu-based release image with APT setup
Dockerfile.alpine	Removed old Alpine-specific file now covered by default Dockerfile
.goreleaser.yaml	Added Ubuntu Dockerfile section, updated image templates
.github/workflows/lint_and_test.yml	Updated CI steps to test the Ubuntu image variant

Comments suppressed due to low confidence (2)

Dockerfile:20

• The default Alpine Dockerfile no longer includes the COPY dockerfilegraph / and ENTRYPOINT ["/dockerfilegraph"] steps, so containers won’t have the binary or entrypoint defined. Re-add those instructions after USER app.

USER app

.goreleaser.yaml:25

• The Alpine image_templates entries have lost their dockerfile: Dockerfile.alpine parent mapping, breaking the YAML structure. Reintroduce the - dockerfile: Dockerfile.alpine block (properly indented) to associate those templates with the Alpine Dockerfile.

-  - dockerfile: Dockerfile.alpine