In shell, a variable is often considered unset even if it is
set to the empty string. In other words,
STOW_DIR= stow [args]
is an idiomatic alternative to writing:
unset STOW_DIR
stow [args]
and it also has the advantage of temporarily "unsetting" STOW_DIR
for a single command.
Therefore we should treat STOW_DIR being set to the empty string
as equivalent to it not being set at all.
Thanks to Cuong Manh Le for highlighting this issue!
Fixes#6 - https://github.com/aspiers/stow/issues/6Closes#5 - https://github.com/aspiers/stow/pull/5
This is more in keeping with the UNIX convention of no output on success,
and is also the way Stow v1.x behaved. Thanks to Adam Sampson for the suggestion.
