Convenience procedure for temporarily changing directories.
The source for this extension is available here.
Usage[procedure] (with-current-directory path thunk)
Changes directory to the given path, calls thunk, and restores the original working directory afterwards.
Note that this procedure is not thread-safe. The current directory is a process-level value, and this extension makes no attempt to preserve thread-specific working directories across interrupts. If the calling thread is preempted or yields before the thunk's body returns, the given path will persist as the process's current working directory at least until the calling thread is resumed.