Bash completion support for remotes in .git/config.

Bash completion support for remotes in .git/config.

Now that Git natively supports remote specifications within the
config file such as:

	[remote "origin"]
		url = ...

we should provide bash completion support "out of the box" for
these remotes, just like we do for the .git/remotes directory.

Also cleaned up the __git_aliases expansion to use the same form
of querying and filtering repo-config as this saves two fork/execs
in the middle of a user prompted completion.  Finally also forced
the variable 'word' to be local within __git_aliased_command.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>