idea: Download 'exiftool' to 'tools::R_user_dir("exiftoolr")'

[trevorld]

• tools::R_user_dir("exiftoolr") should generally be more writable by users than system.file(package = "exiftoolr").

  • In particular the case where exiftoolr is installed by an admin in the shared library of a multi-user server (and hence is owned by "root"). I already have a system install of exiftool so this isn't a problem but my attempt of using install_exiftool() to see what happens failed for this reason.

• Not sure if it would be better to use R_user_dir("exiftoolr", "data") (default) versus R_user_dir("exiftoolr", "config") versus R_user_dir("exiftoolr", "cache") but it probably doesn't matter too much which one is chosen.

• R_user_dir() was introduced in R 4.0.0 so you'd need to bump your R version requirement or use the {backports} version

[JoshOBrien]

@trevorld These are great ideas -- thanks! -- and if you would like to prep a PR implementing them, I'd happily look it over and then merge it. If not, I'll likely get to this eventually, but not for at least a few weeks.

FWIW, using R_user_dir("exiftoolr", "data") makes best sense to me. Also, I'd strongly prefer to not add an R version requirement, so would want to use the version of R_user_dir() made available by backports.