Unblock auto-releases

Last time this ran, GoReleaser built an artefact with the wrong version
- it didn't bump it correctly. It was meant to build 0.1.0-alpha.33, but
it built 0.1.0-alpha.32 instead:
https://github.com/dagger/dagger/runs/4860126130?check_suite_focus=true#step:7:94

This new approach is a simpler and more explicit tag bump by leveraging
the semver-tool directly. A link to this utility is included in the
comments. We version it in this repository so that it is all
self-contained.

We also use the gh CLI tool directly, instead of a GitHub Action that
hides the implementation detail behind Typescript. We now have two very
simple gh CLI invocations that do all that. While we still use the
https://github.com/lewagon/wait-on-check-action GitHub Action to wait
on running checks, and abort if any check failed, I didn't want to
bundle that improvement into this PR - it's already big enough.

As a meaningful improvement, we should have a Dagger package that bumps
versions.  It would have been so much easier to use that Dagger package.
That implies us switching our GitHub Actions to Dagger, which we should
totally do. Small steps ftw!

Next step: run 0.1.0 release manually
Step 2: run 0.2.0-alpha.1 release manually
Step 3: wait for 0.2.0-alpha.2 to be produced automatically, tomorrow.

Pair: @aluzzardi

Signed-off-by: Gerhard Lazu <gerhard@lazu.co.uk>

.github/workflows/auto-release.yml

@@ -20,10 +20,15 @@ on:
     # So we run these at a special time, 9:06. Ask @gerhard about it.
 
   # And it also supports manual triggering:
+  # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#onworkflow_dispatchinputs
   workflow_dispatch:
     inputs:
-      tag:
-        description: 'Custom tag (default bumps last tag) DO NOT prefix with v'
+      release_type:
+        description: 'major|minor|patch|release|prerel'
+        default: 'prerel alpha..'
+        required: true
+      release_version:
+        description: 'Optional release version, e.g. 0.2.0'
         required: false
 
 jobs:
@@ -47,23 +52,30 @@ jobs:
           running-workflow-name: "Bump version, tag & release"
           allowed-conclusions: success
 
-      - name: "Tag so that a new release can be produced"
-        id: tag_version
-        # https://github.com/mathieudutour/github-tag-action
-        uses: mathieudutour/github-tag-action@v6.0
+      - name: "Create next release tag"
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          if [[ -n "${{ github.event.inputs.release_version }}" ]]
+          then
+            next_release_version="v${{ github.event.inputs.release_version }}"
+          else
+            previous_release_version="$(gh api /repos/:owner/:repo/releases --jq '.[0].tag_name')"
+            echo "PREVIOUS RELEASE VERSION: $previous_release_version"
+            # Rather than installing it on every run, we commit it locally so that we have everything we need locally
+            # wget https://raw.githubusercontent.com/fsaintjacques/semver-tool/3.3.0/src/semver
+            # https://github.com/fsaintjacques/semver-tool
+            next_release_version="v$(./semver bump ${{ github.event.inputs.release_type }} $previous_release_version)"
+          fi
+          echo "NEXT RELEASE VERSION: $next_release_version"
+          gh api -X POST /repos/:owner/:repo/git/refs \
+            --field ref="refs/tags/$next_release_version" \
+            --field sha="$GITHUB_SHA"
+
+      - name: "Fetch new tag"
+        uses: actions/checkout@v2
         with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
-          fetch_all_tags: true
-          custom_tag: "${{ github.event.inputs.tag }}"
-          # This is OK for now, but let's revisit this around February 2022
-          release_branches: "there_are_only_prereleases_for_now"
-          # When we start auto-bumping patches/minors, consider removing pre-releases
-          pre_release_branches: "main"
-          append_to_pre_release_tag: "alpha"
-          # Set to true when you are testing / experimenting
-          dry_run: false
-        # This may be of interest when we need more control over the version bumps
-        # https://github.com/craig-day/compute-tag
+          fetch-depth: 0
 
       - name: "Install Go"
         uses: actions/setup-go@v2