Don't store remote and local branch names in shell variables, but query
them live using git commands instead. This avoids git commands being
issued by subcommands that do not necessarily require an existing Git repo
to be initialized (i.e. git-flow init).
diff --git a/git-flow-support b/git-flow-support
index 804a01d..99baf37 100644
--- a/git-flow-support
+++ b/git-flow-support
@@ -34,7 +34,7 @@
 	local support_branches
 	local current_branch
 	local short_names
-	support_branches=$(echo "$LOCAL_BRANCHES" | grep "^$PREFIX")
+	support_branches=$(echo "$(gitflow_local_branches)" | grep "^$PREFIX")
 	if [ -z "$support_branches" ]; then
 		warn "No support branches exist."
 		exit 0