show-branch: don't <COLOR></RESET> for space characters

show-branch: don't <COLOR></RESET> for space characters

Change the colored output introduced in ab07ba2a24 (show-branch: color
the commit status signs, 2009-04-22) to not color and reset each
individual space character we use for padding. The intent is to color
just the "!", "+" etc. characters.

This makes the output easier to test, so let's do that now. The test
would be much more verbose without a color/reset for each space
character. Since the coloring cycles through colors we previously had
a "rainbow of space characters".

In theory this breaks things for anyone who's relying on the exact
colored output of show-branch, in practice I'd think anyone parsing it
isn't actively turning on the colored output.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>