R: sourcing files using a relative path

After a discussion with @hadley on GitHub, I realized that my question goes against the common development patterns in R.

It seems that in R files that are sourced often assume that the working directory (getwd()) is set to the directory they are in. To make this work, source has a chdir argument whose default value is FALSE. When set to TRUE, it will change the working directory to the directory of the file being sourced.

In summary:

1. Assume that source is always relative because the working directory of the file being sourced is set to the directory where the file is.

2. To make this work, always set chdir=T when you source files from another directory, e.g., source('lib/stats/big_stats.R', chdir=T).

For convenient sourcing of entire directories in a predictable way I wrote sourceDir, which sources files in a directory in alphabetical order.

sourceDir <- function (path, pattern = "\\.[rR]$", env = NULL, chdir = TRUE) 
{
    files <- sort(dir(path, pattern, full.names = TRUE))
    lapply(files, source, chdir = chdir)
}