res/build.sh: use lowdown instead of pandoc for mandoc output.

Given that pandoc is a haskell program, depending on it is bad due to
bootstrap and general platform compatibility concerns. Lowdown output
looks just as good if not better.

The ideal build will have the git repository available to it; builds
without the git repo will use SOURCE_DATE_EPOCH from the environment.

README.md

@@ -13,7 +13,7 @@ Void packages:
 
 - `mdBook`
 - `findutils`
-- `pandoc`
+- `lowdown` (version 0.8.1 or greater)
 - `texlive`
 - `perl`
 - `perl-JSON`

res/build.sh

@@ -6,20 +6,33 @@
 set -e
 PATH="$PWD/res:$PATH"
 
+if [ -z "$SOURCE_DATE_EPOCH" ]; then
+    export SOURCE_DATE_EPOCH=$(git log --pretty='%ct' -1)
+    if [ -z "$SOURCE_DATE_EPOCH" -a "$BUILD_MANPAGES" = 1 ]; then
+      echo "git or SOURCE_DATE_EPOCH are needed to build man pages!"
+      exit 1
+    fi
+fi
+
 # Build HTML mdbook
 echo "Building mdBook"
 mdbook build
 
-
 if [ "$BUILD_MANPAGES" = "1" ]; then
     # Build mandoc version
     echo "Building man pages"
-    mkdir -p mandoc
     cd src
 
     find . -type d -exec mkdir -p "../mandoc/{}" \;
+
     find . -type f -name "*.md" -exec sh -c \
-        'file="{}"; filew="${file%.md}"; pandoc -V "title=${filew##*/}" -V section=7 -V "header=Void Docs" -s -o "../mandoc/${filew}.7" "$file"' \;
+      'file="{}"; filew="${file%.md}"; \
+          man_date="$(git log --pretty=%cs -1 "$file" 2>/dev/null || date -d "@$SOURCE_DATE_EPOCH" +%F)";
+          lowdown -Tman \
+          ${man_date:+-m "date: $man_date"} \
+          -m "title: ${filew##*/}" \
+          -m "section: 7" -m "source: Void Docs" -m "volume: Void Docs" \
+          -s -o "../mandoc/${filew}.7" "$file"' \;
 
     cd -
 fi