runGist amended for Windows

runGist.r

#all code credit goes to https://github.com/rstudio/shiny/
#this is a simple two line change to deal with Windows tar difficulties
#thanks to http://www.worthinstalling.com/2006/06/command-line-compression-for-windows.html for the good explanation

#to use this install bsdtar in Windows
#in R require(Shiny) and then run this to override runGist

runGist <- function (gist, port = 8100L, launch.browser = getOption("shiny.launch.browser", 
                                                         interactive())) 
{
  gistUrl <- if (is.numeric(gist) || grepl("^[0-9a-f]+$", gist)) {
    sprintf("https://gist.github.com/gists/%s/download", 
            gist)
  }
  else if (grepl("^https://gist.github.com/([0-9a-f]+)$", gist)) {
    paste(sub("https://gist.github.com/", "https://gist.github.com/gists/", 
              gist), "/download", sep = "")
  }
  else {
    stop("Unrecognized gist identifier format")
  }
  filePath <- tempfile("shinygist", fileext = ".tar.gz")
  if (download.file(gistUrl, filePath, mode = "wb", quiet = TRUE) != 
    0) 
    stop("Failed to download URL ", gistUrl)
  on.exit(unlink(filePath))
  dirname <- untar(filePath, list = TRUE, tar="bsdtar.exe")[1]
  untar(filePath, exdir = dirname(filePath),tar="bsdtar.exe")
  appdir <- file.path(dirname(filePath), dirname)
  on.exit(unlink(appdir, recursive = TRUE))
  shiny::runApp(appdir, port = port, launch.browser = launch.browser)
}