Unsure about the purpose of the HISTORY_SIZE and HISTFILE_SIZE variables
When giving the manual a second read, I couldn't figure out how these variables differ, and how do they work exactly, since they don't seem to appear, neither in Ion's code (besides giving them default values), nor in liner's.
Also, it's not clear to me, why, as stated in the docs, their values should be the same, while being both necessary.