Determine the path of the executing script.
Compatible with several popular GUIs:
‘Rgui’
‘RStudio’ (including background jobs)
‘Positron’
‘VSCode’ + ‘REditorSupport’
‘Jupyter’
‘Rscript’
      (shell)
Compatible with several functions and packages:
debugSource() in ‘RStudio’
box::use()
plumber::plumb()
Iris Simmons [aut, cre]
Maintainer: Iris Simmons <ikwsimmo@gmail.com>
The most important functions from package:this.path are
  this.path(), this.dir(), here(),
  and this.proj():
this.path() returns the normalized path of the script
      in which it is written.
this.dir() returns the directory of
      this.path().
here() constructs file paths against
      this.dir().
this.proj() constructs file paths against the project
      root of this.dir().
New additions include:
LINENO() returns the line number of the executing
      expression.
shFILE() looks through the command line arguments,
      extracting FILE from either of the following: -f
      FILE or --file=FILE
set.sys.path() implements this.path() for
      any source()-like functions outside of the builtins.
with_init.file() allows this.path() and related
      to be used in a user profile.
package:this.path also provides functions for constructing and manipulating file paths:
path.join(), basename2(), and
      dirname2() are drop in replacements for
      file.path(), basename(), and
      dirname() which better handle drives and
      network shares.
splitext(), removeext(),
      ext(), and ext<-() split a path into root and
      extension, remove a file extension, get an extension, or set an extension
      for a file path.
path.split(), path.split.1(), and
      path.unsplit() split the path to a file into components.
relpath(), rel2here(), and
      rel2proj() turn absolute paths into relative paths.