completion: fix alias listings with newlines

completion: fix alias listings with newlines

Aliases with newlines have been a problem since commit 56fc25f (Bash
completion support for remotes in .git/config., 2006-11-05). The chance
of the problem occurring has been slim at best, until commit 518ef8f
(completion: Replace config --list with --get-regexp, 2009-09-11)
removed the case statement introduced by commit 56fc25f. Before removing
the case statement, most aliases with newlines would work unless they
were specially crafted as follows

[alias]
	foo = "log -1 --pretty='format:%s\nalias.error=broken'"

After removing the case statement, a more benign alias like

[alias]
	whowhat = "log -1 --pretty='format:%an <%ae>\n%s'"
	wont-complete = ...

would cause the completion to break badly.

For now, revert the removal of the case statement until someone comes up
with a better way to get keys from git-config.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Acked-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>