Docs/cookbook: add an R + latex example.

This shows how to dynamically generate a plot in R+ggplot2, then embed
it into a latex document, and compile it to pdf, all with proper
autodependencies.

Documentation/cookbook/latex/default.runtex.do

@@ -0,0 +1,58 @@
+# latex produces log output on stdout, which is
+# not really correct.  Send it to stderr instead.
+exec >&2
+
+# We depend on both the .latex file and its .deps
+# file (which lists additional dependencies)
+redo-ifchange "$2.latex" "$2.deps"
+
+# Next, we have to depend on each dependency in
+# the .deps file.
+cat "$2.deps" | xargs redo-ifchange
+
+tmp="$2.tmp"
+rm -rf "$tmp"
+mkdir -p "$tmp"
+
+# latex generates eg.  the table of contents by
+# using a list of references ($2.aux) generated
+# during its run.  The first time, the table of
+# contents is empty, so we have to run again. 
+# But then the table of contents is non-empty,
+# which might cause page numbers to change, and
+# so on.  So we have to keep re-running until it
+# finally stops changing.
+touch "$tmp/$2.aux.old"
+ok=
+for i in $(seq 5); do
+    latex --halt-on-error \
+        --output-directory="$tmp" \
+        --recorder \
+        "$2.latex" </dev/null
+    if diff "$tmp/$2.aux.old" \
+            "$tmp/$2.aux" >/dev/null; then
+        # .aux file converged, so we're done
+        ok=1
+        break
+    fi
+    echo
+    echo "$0: $2.aux changed: try again (try #$i)"
+    echo
+    cp "$tmp/$2.aux" "$tmp/$2.aux.old"
+done
+
+if [ "$ok" = "" ]; then
+    echo "$0: fatal: $2.aux did not converge!"
+    exit 10
+fi
+
+# If the newly produced .dvi disappears, we need
+# to redo.
+redo-ifchange "$tmp/$2.dvi"
+
+# With --recorder, latex produces a list of files
+# it used during its run.  Let's depend on all of
+# them, so if they ever change, we'll redo.
+grep ^INPUT "$tmp/$2.fls" |
+    cut -d' ' -f2 |
+    xargs redo-ifchange