fetch tests: refactor in preparation for testing tag pruning

In a subsequent commit this function will learn to test for tag
pruning, prepare for that by making space for more variables, and
making it clear that "expected" here refers to branches.

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

t/t5510-fetch.sh

@@ -549,9 +549,12 @@ set_config_tristate () {
 }
 
 test_configured_prune () {
-	fetch_prune=$1 remote_origin_prune=$2 cmdline=$3 expected=$4
+	fetch_prune=$1
+	remote_origin_prune=$2
+	cmdline=$3
+	expected_branch=$4
 
-	test_expect_success "prune fetch.prune=$1 remote.origin.prune=$2${3:+ $3}; $4" '
+	test_expect_success "prune fetch.prune=$1 remote.origin.prune=$2${3:+ $3}; branch:$4" '
 		# make sure a newbranch is there in . and also in one
 		git branch -f newbranch &&
 		(
@@ -572,7 +575,7 @@ test_configured_prune () {
 			set_config_tristate remote.origin.prune $remote_origin_prune &&
 
 			git fetch $cmdline &&
-			case "$expected" in
+			case "$expected_branch" in
 			pruned)
 				test_must_fail git rev-parse --verify refs/remotes/origin/newbranch
 				;;