ui-log: Line-wrap long commit subjects when showmsg is enabled

ui-log: Line-wrap long commit subjects when showmsg is enabled

When showmsg is disabled ui-log truncates long commit subjects. This is good.
However, the same is not desirable when showmsg is enabled, since you then
end up with a truncated commit subject followed by the rest of the commit
message below.

Instead, when showmsg is enabled (and we're using all this space to display
the entire commit message, anyway), line-wrap the commit subject instead of
truncating it.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>