Use same settings as base R package tools to compute dependencies

[eddelbuettel]

deepdep defaults to the (deprecated, but still used) Depends as well as Imports.

That is non-standard in the sense that base R package tools also use LinkingTo (which is equally 'non-negotiable') and optionally folds in Suggests and Enhances

Obviously we can add this by hand via dependency_type= but it is ... tedious. I suggest to either expand the default and/or support use of getOption() with a fallback (which is a scheme I use and like in a few of my packages). Happy to send a PR if that is seen as suitable.

The help for eg tools::package_dependencie has a good discussion, mimicking its options 'all' and 'most' and then 'strong' as the (new) default would be really nice:

which: a character vector listing the types of dependencies, a
subset of ‘c("Depends", "Imports", "LinkingTo", "Suggests",
"Enhances")’. Character string ‘"all"’ is shorthand for that
vector, character string ‘"most"’ for the same vector without
‘"Enhances"’, character string ‘"strong"’ (default) for the
first three elements of that vector.

Thanks for creating the package.

[DominikRafacz]

Thanks for your suggestions! I think those improvements will be very useful.