Automatically update Docker Hub descriptions

.github/workflows/dockerhub-description.yaml

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+name: Update Docker Hub Description
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - versions.md
+      - README.md
+      - docs/**/*
+
+  workflow_dispatch:
+
+jobs:
+  updateDescriptions:
+    name: Update description
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        image:
+          - minimal
+          - core
+          - latex
+          - extra
+          - typst
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup pandoc
+        uses: pandoc/actions/setup@v1
+
+      - name: Short description
+        id: config
+        run: |
+          printf 'short_description=%s\n' \
+            "$(pandoc lua docs/scripts/short-description.lua \
+                      ${{ matrix.image }})" \
+            >> $GITHUB_OUTPUT
+
+
+      - name: Generate README files
+        run: |
+          make docs-${{ matrix.image }} > /tmp/README.${{ matrix.image }}.md
+
+      - name: Update ${{ matrix.image }}
+        uses: peter-evans/dockerhub-description@e98e4d1628a5f3be2be7c231e50981aee98723ae
+        with:
+          username: ${{ secrets.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_TOKEN }}
+          repository: pandoc/${{ matrix.image }}
+          readme-filepath: /tmp/README.${{ matrix.image }}.md
+          short-description: ${{ steps.config.outputs.short_description }}

docs/scripts/short-description.lua

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+--- short-description.lua: get the short description for a repository
+--- Author: Albert Krewinkel <albert+pandoc@tarleb.com>
+--- License: MIT
+
+local io     = require 'io'
+local pandoc = require 'pandoc'
+
+local stringify = pandoc.utils.stringify
+
+--- Command-line arguments
+local arg = arg
+
+--- The image type / repository name
+local repo = assert(arg[1], "Repository name is required")
+local inputfile = arg[2] or 'docs/short-descriptions.md'
+local fh = io.open(inputfile, 'r')
+local contents = fh:read('a')
+fh:close()
+
+local doc = pandoc.read(contents)
+
+assert(doc.meta[repo], "No description found for repository " .. repo)
+
+print(stringify(doc.meta[repo]))

docs/short-descriptions.md

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+---
+minimal: >-
+  Minimal image for pandoc, the universal document converter.
+
+core: >-
+  Official pandoc image with image conversion tools and pandoc-crossref.
+
+latex: >-
+  Official pandoc image with pandoc, pandoc-crossref, and a minimal LaTeX
+  installation.
+
+extra: >-
+  Large pandoc image with many LaTeX extras, including popular fonts and the
+  "Eisvogel" template.
+
+typst: >-
+  Document conversion with pandoc, pandoc-crossref, and Typst.
+---