fix(ci): scope nightly release notes to commits since last release

.github/workflows/ci-main.yml

@@ -44,6 +44,7 @@ jobs:
       name:       ${{ steps.meta.outputs.name }}
       prerelease: ${{ steps.meta.outputs.prerelease }}
       latest:     ${{ steps.meta.outputs.latest }}
+      lastTag:    ${{ steps.meta.outputs.lastTag }}
     steps:
       - uses: actions/checkout@v4
         with: { fetch-depth: 0 }    # full history: version = git describe
@@ -82,9 +83,15 @@ jobs:
             "prerelease=true"                 >> $env:GITHUB_OUTPUT
             "latest=false"                    >> $env:GITHUB_OUTPUT
           }
+          # Last official release tag reachable from HEAD (e.g. v2.0.0). Used to pin the
+          # base for nightly release-notes so they cover only "since the last release"
+          # instead of the whole history. Match v<digit> to skip legacy junk tags
+          # (OpenXcomCoop_*, v-non-numeric). Empty on a repo with no release tag yet.
+          $lastTag = (git describe --tags --abbrev=0 --match "v[0-9]*" 2>$null)
+          "lastTag=$lastTag"       >> $env:GITHUB_OUTPUT
           "version=$v"             >> $env:GITHUB_OUTPUT
           "gitSuffix=$gitSuffix"   >> $env:GITHUB_OUTPUT
-          Write-Host "version: $v$gitSuffix"
+          Write-Host "version: $v$gitSuffix (base: $lastTag)"
 
   build:
     needs: meta
@@ -361,24 +368,39 @@ jobs:
           prerelease:  ${{ needs.meta.outputs.prerelease }}
           make_latest: ${{ needs.meta.outputs.latest }}
           files: ${{ env.ASSETS }}      # x64 zip + WinXP zip + Linux tarball, one call
-          # release -> curated notes from CHANGELOG.md; nightly -> auto-generated
+          # release -> curated notes from CHANGELOG.md; nightly -> generated by the next
+          # step, pinned to previous_tag_name (GitHub's auto base picks the whole history
+          # for the non-semver `nightly` tag -> notes grow forever). Publish with an empty
+          # body; the strip step below fills it in.
           body_path: ${{ needs.meta.outputs.channel == 'release' && 'release-notes.md' || '' }}
-          generate_release_notes: ${{ needs.meta.outputs.channel != 'release' }}
+          generate_release_notes: false
 
-      - name: Strip 'New Contributors' + author handles from nightly notes
+      - name: Generate nightly notes since last release + strip authorship
         if: needs.meta.outputs.channel == 'nightly'
         shell: pwsh
         env:
           GH_TOKEN: ${{ github.token }}
         run: |
+          # Generate the "What's Changed" list ourselves, pinned to the last official
+          # release. GitHub's auto base-selection can't order the non-semver `nightly`
+          # tag against the legacy junk tags, so it diffs from ~repo start and the notes
+          # grow without bound. previous_tag_name = last release => notes cover exactly
+          # the commits since that release. Empty lastTag (no release yet) falls back to
+          # GitHub's default base.
+          $prev = "${{ needs.meta.outputs.lastTag }}"
+          $call = @('api', "repos/$env:GITHUB_REPOSITORY/releases/generate-notes",
+                    '-f', 'tag_name=nightly',
+                    '-f', 'target_commitish=${{ github.sha }}')
+          if ($prev) { $call += @('-f', "previous_tag_name=$prev") }
+          Write-Host "generate-notes base: $(if ($prev) { $prev } else { '(auto)' })"
+          # gh returns the body as a string[] (one element per line). Without an explicit
+          # -join, PowerShell coerces it to a single string joined with SPACES, which
+          # destroys every newline (notes render as one run-on paragraph) and makes the
+          # regexes below never match. Always -join "`n" first.
+          $body  = (& gh @call --jq '.body') -join "`n"
           # "New Contributors" is meaningless on a rolling tag: GitHub recomputes it each
-          # run against a shifting base (the last release tag) and flags even the original
-          # dev as "new". Remove that section, keeping "## What's Changed" + "Full Changelog".
-          # NOTE: gh returns the body as a string[] (one element per line). Without an
-          # explicit -join, PowerShell coerces it to a single string joined with SPACES,
-          # which destroys every newline (notes render as one run-on paragraph) and makes
-          # the regex below never match. Always -join "`n" first.
-          $body  = (gh release view nightly --repo "$env:GITHUB_REPOSITORY" --json body --jq '.body') -join "`n"
+          # run against a shifting base and flags even the original dev as "new". Remove
+          # that section, keeping "## What's Changed" + "Full Changelog".
           $clean = [regex]::Replace($body, "(?s)\r?\n?## New Contributors\r?\n(?:\*.*\r?\n?)*\r?\n?(?=\*\*Full Changelog\*\*)", "`n`n")
           # Drop the "by @author" credit from each "What's Changed" bullet - the notes
           # should describe the change, not the committer.