git-checkout: fix branch name output from the command

When switching branches with "git checkout", we internally did $arg^0
(aka $arg^{commit}) suffix but there was no need to.

The improvement is easily visible in the change to an existing
test t/3200-branch.sh in this commit; it was expecting rather
ugly message.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-checkout.sh

@@ -53,7 +53,7 @@ while [ "$#" != "0" ]; do
 				exit 1
 			fi
 			new="$rev"
-			new_name="$arg^0"
+			new_name="$arg"
 			if git-show-ref --verify --quiet -- "refs/heads/$arg"
 			then
 				branch="$arg"

t/t3200-branch.sh

@@ -48,7 +48,7 @@ test_expect_success \
 	 test ! -f .git/logs/refs/heads/d/e/f'
 
 cat >expect <<EOF
-0000000000000000000000000000000000000000 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	checkout: Created from master^0
+0000000000000000000000000000000000000000 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	checkout: Created from master
 EOF
 test_expect_success \
     'git checkout -b g/h/i -l should create a branch and a log' \