write_xlsx.md
In xlr: Create Table Summaries and Export Neat Tables to 'Excel'

write_xlsx() gives an error when append and overwrite is true

Code
  write_xlsx(mtcars, tmp_file, sheet_name = "Test", TOC = FALSE, overwrite = TRUE,
    append = TRUE)
Condition
  Error in `write_xlsx()`:
  ! You can only overwrite or append a file, not both.

write_xlsx() sends a message when it appends a file

Code
  write_xlsx(mtcars, tmp_file, sheet_name = "Test", overwrite = FALSE, append = TRUE)
Message
  i Appending file:

write_xlsx() sends a message when it overwrites a file

Code
  write_xlsx(mtcars, tmp_file, sheet_name = "Test", overwrite = TRUE, append = FALSE)
Message
  i Overwriting file:

write_xlsx() sends an error when it is not allowed to modify a file

Code
  write_xlsx(mtcars, tmp_file, sheet_name = "Test", overwrite = FALSE, append = FALSE)
Condition
  Error in `write_xlsx()`:
  ! Cannot write file, already exists!