Selective recompilation

[edemaine]

• If generated SVG is equal to the existing .svg file, don't bother writing it
• If generated SVG didn't change, don't generate PDF/PNG via Inkscape. This will be a huge time savings for repeated runs.
• If generated SVG is equal to the existing .tex file, don't bother writing it
• If all mapping files + drawing file are older than generated SVG/TeX and SVG Tiler itself, don't even do .svg generation.
  • -f/--force option
• Ideally, Excel spreadsheets have "last modified" metadata for each sheet, and then you can do this at the sheet level. (But maybe not necessary given the "skip if .svg unchanged", because the slowest part is probably the initial loading of the spreadsheet archive.)