Change nightlies versioning from v4.2.0+2023-08-23 to `v4.2.0-night…

…ly.2023-08-23` (mastodon#26626)

.github/workflows/build-nightly.yml

@@ -16,7 +16,7 @@ jobs:
  env:
  TZ: Etc/UTC
  run: |
- echo mastodon_version_suffix=nightly-$(date +'%Y-%m-%d')>> $GITHUB_OUTPUT
+ echo mastodon_version_suffix=nightly.$(date +'%Y-%m-%d')>> $GITHUB_OUTPUT
  outputs:
  suffix: ${{ steps.version_vars.outputs.mastodon_version_suffix }}
 
@@ -29,8 +29,8 @@ jobs:
  push_to_images: |
  tootsuite/mastodon
  ghcr.io/mastodon/mastodon
- # The `+` is important here, result will be v4.1.2+nightly-2022-03-05
- version_suffix: +${{ needs.compute-suffix.outputs.suffix }}
+ # The `-` is important here, result will be v4.1.2-nightly.2022-03-05
+ version_suffix: -${{ needs.compute-suffix.outputs.suffix }}
  labels: |
  org.opencontainers.image.description=Nightly build image used for testing purposes
  flavor: |