merge: remove always-the-same "verbose" arguments

merge: remove always-the-same "verbose" arguments

Simplify the code that builds the arguments for the "read-tree"
invocation in reset_hard() and read_empty() to remove the "verbose"
parameter.

Before 172b6428d06 (do not overwrite untracked during merge from
unborn branch, 2010-11-14) there was a "reset_hard()" function that
would be called in two places, one of those passed a "verbose=1", the
other a "verbose=0".

After 172b6428d06 when read_empty() was split off from reset_hard()
both of these functions only had one caller. The "verbose" in
read_empty() would always be false, and the one in reset_hard() would
always be true.

There was never a good reason for the code to act this way, it
happened because the read_empty() function was a copy/pasted and
adjusted version of reset_hard().

Since we're no longer conditionally adding the "-v" parameter
here (and we'd only add it for "reset_hard()" we'll be able to move to
a simpler and safer run-command API in the subsequent commit.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Taylor Blau <me@ttaylorr.com>