We take pains to determine the longest command beforehand, so that we
can align the category column after printing the command names.
However, then we re-use that value when printing the aliases. If any
alias name is longer than the longest command name, we consequently try
to add a negative number of spaces (but `mput_char()` does not expect
any negative values and simply decrements until the value is 0, i.e.
it tries to add close to 2**31 spaces).
Let's fix this by adjusting the `longest` variable before printing the
aliases.
This fixes https://github.com/git-for-windows/git/issues/1975.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>