Github: Add and replace snap build job

[roosterfish]

Migrates the build job from github.com/canonical/microcloud-pkg-snap. Aligns with the build job from LXD.

To stay in line with LXD, I would propose using the same format for release-* branches even though MicroCloud uses vX-edge scheme for the version branches.

[Copilot]

Pull request overview

Migrates the GitHub Actions “snap” job to the newer Launchpad snap build flow (aligned with the approach used by LXD), replacing the previous microcloud-pkg-snap-based triggering.

Changes:

• Updates the snap job to use canonical/lxd-pkg-snap/.github/actions/lp-snap-build with the MicroCloud Launchpad repo.
• Adds branch mapping logic (edge vs candidate) and derives snap version/grade from version/version.go and branch naming patterns.
• Pushes updates to the Launchpad branches, including repository packing/gc before pushing.

Comments suppressed due to low confidence (1)

.github/workflows/tests.yml:379

• Same issue as above: || true suppresses grep errors (exit 2) as well as "no matches" (exit 1). Count with awk so missing/unreadable files still fail clearly.

            # Fail unless exactly one `grade: devel` line exists, then replace it.
            match_count="$(grep -cxF 'grade: devel' snapcraft.yaml || true)"
            if [ "${match_count}" -ne 1 ]; then

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

snap/snapcraft.yaml:99

• go get ./... during the snap build can update go.mod/go.sum (and potentially upgrade deps), making the snap build non-reproducible. Prefer downloading modules without changing the module graph.

      set -ex

      # Download the dependencies
      go get -v -tags=agent ./...

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

snap/snapcraft.yaml:97

• go get ... ./... is not a pure “download deps” step and can update go.mod/go.sum, reducing build reproducibility. Use go mod download to fetch the pinned module graph without modifying module files.

      go get -v -tags=agent ./...

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

snap/snapcraft.yaml:97

• override-pull uses go get -v -tags=agent ./... to “download dependencies”. In module mode, go get ./... can update go.mod/go.sum and may invoke package loading that triggers CGO processing/build steps, which is fragile this early in the lifecycle (before the build env/CGO flags are set) and can fail on cgo-based deps. Prefer go mod download (or go mod download -x) here to fetch modules without attempting to build/update them.

    override-pull: |
      craftctl default
      set -ex

      # Download the dependencies
      go get -v -tags=agent ./...

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

snap/snapcraft.yaml:97

• override-pull runs go get ./... to “download dependencies”. go get is intended for changing module requirements and can unexpectedly rewrite go.mod/go.sum during the pull step. Use a non-mutating download step (e.g. go mod download) to populate the module cache instead.

      # Download the dependencies
      go get -v -tags=agent ./...