Add README.md on how to extract and compile code examples

doc/generic/pgf/README.md

@@ -0,0 +1,52 @@
+# Extract and compile code exmples
+
+```bash
+# Set up the directories for example code extraction and compilatiom
+mkdir -p ~/tmp/mwe/plots
+mkdir -p ~/tmp/mwe/generic/pgf/plots
+
+cd ~/tmp/mwe
+ln -s ~/github.com/pgf/doc/generic/pgf/images
+
+cd ~/tmp/mwe/generic/pgf
+ln -s ~/github.com/pgf/doc/generic/pgf/images
+
+# Clean up
+find ~/tmp/mwe -name '*.tex' -o -name '*.aux' -o -name '*.log' -o -name '*.gz' -o -name '*.pdf' | xargs rm
+
+# Extract code examples to ~/tmp/mwe
+cd ~/tmp
+texlua ~/github.com/pgf/doc/generic/pgf/extract.lua ~/github.com/pgf/tex ~/github.com/pgf/doc ~/tmp/mwe
+
+# Delete the irrelevant files
+find mwe -name '*finder*.tex' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'very simple example layout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'print_lines_on_output' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'social degree layout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'animated binary tree layout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'SugiyamaLayout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'BalloonLayout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'CircularLayout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'FMMMLayout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l 'PlanarizationLayout' | xargs rm
+find mwe -name '*.tex' | xargs grep -l '<g id="pgf3"  prefix=" automata: http://www.tcs.uni-luebeck.de/ontologies/automata/ ">' | xargs rm
+
+# Compile all the code examples
+cd mwe
+n=1
+N=$(find . -name '*.tex' | wc -l)
+
+time for i in $(find . -name '*.tex'); do
+    echo -n "Processing $n/$N $i"
+    if [ -f "${i%%.tex}.pdf" ]; then
+        echo -n " Skipped." # skip existing
+    else
+        lualatex -interaction=batchmode -shell-escape -halt-on-error "$i" > /dev/null
+        if [ "x$?" == "x1" ]; then
+            echo -n " Failed!"
+        fi
+    fi
+    echo ""
+    n=$((n+1))
+done 2>&1 | tee ./compilation.log
+```