pb_upload: Upload data to an existing release
In piggyback: Managing Larger Data on a GitHub Repository

NOTE: you must first create a release if one does not already exists.

pb_upload(
  file,
  repo = guess_repo(),
  tag = "latest",
  name = NULL,
  overwrite = "use_timestamps",
  use_timestamps = NULL,
  show_progress = TRUE,
  .token = get_token(),
  dir = "."
)

`file`	path to file to be uploaded
`repo`	Repository name in format "owner/repo". Will guess the current repo if not specified.
`tag`	tag for the GitHub release to which this data should be attached.
`name`	name for uploaded file. If not provided will use the basename of `file` (i.e. filename without directory)
`overwrite`	overwrite any existing file with the same name already attached to the on release? Defaults to `use_timestamps`, only overwriting those files which are older. Set to `TRUE` to always overwrite, or `FALSE` to never overwrite existing files.
`use_timestamps`	DEPRECATED. please use `overwrite="use_timestamps"`
`show_progress`	logical, show a progress bar be shown for uploading? Defaults to `TRUE`.
`.token`	GitHub authentication token. Typically set from an environmental variable, e.g. in a `.Renviron` file or with `Sys.setenv(GITHUB_TOKEN = "xxxxx")`, which helps prevent accidental disclosure of a secret token when sharing scripts.
`dir`	directory relative to which file names should be based.

## Not run: 
# Needs your real token to run

readr::write_tsv(mtcars,"mtcars.tsv.xz")
pb_upload("mtcars.tsv.xz", "cboettig/piggyback-tests")

## End(Not run)