chore: fix up ghcr tags (#3438)

use `latest` for latest release, `dev` for continuous, and tag dev
builds with `-dev`. also remove the 'master' tag since that's redundant
with `dev`.

.github/workflows/ghcr.yml

@@ -45,17 +45,21 @@ jobs:
           pip install .
           echo "VYPER_VERSION=$(PYTHONPATH=. python vyper/cli/vyper_compile.py --version)" >> "$GITHUB_ENV"
 
+      - name: generate tag suffix
+        if: ${{ github.event_name != 'release' }}
+        run: echo "VERSION_SUFFIX=-dev" >> "$GITHUB_ENV"
+
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@v4
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
-          flavor: |
-            latest=true
           tags: |
-            type=ref,event=branch
             type=ref,event=tag
-            type=raw,value=${{ env.VYPER_VERSION }}
+            type=raw,value=${{ env.VYPER_VERSION }}${{ env.VERSION_SUFFIX }}
+            type=raw,value=dev,enable=${{ github.ref == 'refs/heads/master' }}
+            type=raw,value=latest,enable=${{ github.event_name == 'release' }}
+
 
       - name: Login to ghcr.io
         uses: docker/login-action@v2