docs: add code for generating documentation from all old versions of dokku

This generates the appropriate versions for our usage, in addition to ensuring the markdown is of a format that mkdocs understands.

contrib/build-docs

@@ -0,0 +1,94 @@
+#!/usr/bin/env bash
+set -eo pipefail
+
+readonly ROOT_DIR="$(cd "$(dirname "$(dirname "${BASH_SOURCE[0]}")")" && pwd)"
+
+main() {
+  pushd "$ROOT_DIR" >/dev/null || return 1
+  rm -rf docs-main tmp/docs-source tmp/docs-build/docs # tmp/docs-build
+  mkdir -p tmp/docs-build
+  cp -r docs docs-main
+
+  git clone https://github.com/dokku/dokku.git tmp/docs-source
+
+  rm -rf docs/assets
+  mkdir -p docs/assets
+  cp -r docs-main/assets/favicons docs/assets/favicons
+  cp -r docs-main/assets/dokku-logo.svg docs/assets/dokku-logo.svg
+
+  rm -rf tmp/docs-build/assets
+  cp -r docs-main/assets tmp/docs-build/assets
+
+  make docs-build
+  mv site tmp/docs-build/docs
+  mv docs/home.html tmp/docs-build/index.html
+  sed -i.bak "s/{{NAME}}~{{REF}}/docs/g" tmp/docs-build/index.html && rm tmp/docs-build/index.html.bak
+  sed -i.bak "s/{{NAME}}/docs/g" tmp/docs-build/index.html && rm tmp/docs-build/index.html.bak
+
+  jq -C -r '.["max-versions"][]' docs-main/assets/versions.json | while read -r current_version; do
+    major="$(echo "$current_version" | cut -d'.' -f1)"
+    minor="$(echo "$current_version" | cut -d'.' -f2)"
+    patch="$(echo "$current_version" | cut -d'.' -f3)"
+    while true; do
+      if [[ "$patch" -lt 0 ]]; then
+        break
+      fi
+      version="${major}.${minor}.${patch}"
+      echo "version: ${major}.${minor}.${patch}"
+
+      if [[ "$major" -lt 1 ]]; then
+        if [[ "$current_version" != "$version" ]] && [[ "$minor" -lt 28 ]]; then
+          rm -rf "tmp/docs-build/docs~v${version}"
+          patch=$((patch - 1))
+          continue
+        fi
+      fi
+
+      if [[ -d "tmp/docs-build/docs~v${version}" ]]; then
+        patch=$((patch - 1))
+        continue
+      fi
+
+      git -C tmp/docs-source checkout -- .
+      git -C tmp/docs-source checkout "tags/v${version}" -b "v${version}-branch"
+      rm -rf docs
+      mv tmp/docs-source/docs docs
+
+      rm -rf docs/assets
+      mkdir -p docs/assets
+      cp -r docs-main/assets/favicons docs/assets/favicons
+      cp -r docs-main/assets/dokku-logo.svg docs/assets/dokku-logo.svg
+
+      cp -r docs-main/_build docs/_build
+      cp -r docs-main/_overrides docs/_overrides
+      git checkout -- mkdocs.yml
+      sed -i.bak "s/site_dir: site/site_dir: docs~v$version/g" mkdocs.yml && rm mkdocs.yml.bak
+      if [[ ! -f docs/template.html ]]; then
+        if [[ "$patch" -eq 0 ]]; then
+          break
+        fi
+
+        continue
+      fi
+
+      if ! make docs-build; then
+        continue
+      fi
+
+      if [[ -d "docs~v${version}" ]]; then
+        mv "docs~v${version}" "tmp/docs-build/docs~v${version}"
+      fi
+
+      if [[ "$patch" -eq 0 ]]; then
+        break
+      fi
+      patch=$((patch - 1))
+    done
+  done
+
+  rm -rf docs
+  mv docs-main docs
+  git checkout -- mkdocs.yml docs
+}
+
+main "$@"