scripts/mkimage-yaml: fix branch

we need get the branch from tag instead of git branch, because we
generate releasecandidates and the first stable release from git master
and only do the git branch after the release is done.

scripts/mkimage-yaml.sh

@@ -23,14 +23,20 @@ done
 
 set -- $opt "$@"
 
-releasedir="$branch/releases/$arch"
 if [ -z "$branch" ]; then
-	git_branch="$(git rev-parse --abbrev-ref HEAD)"
-	case "$git_branch" in
-	*-stable) branch=${git_branch%-stable};;
-	*) branch=edge;;
+	case "$release" in
+	*.*.*_alpha*|*.*.*_beta*) branch=edge;;
+	*.*.*) branch=${release%.*}; branch="v${branch#v}";;
+	*)
+		git_branch="$(git rev-parse --abbrev-ref HEAD)"
+		case "$git_branch" in
+		*-stable) branch=${git_branch%-stable};;
+		*) branch=edge;;
+		esac
+		;;
 	esac
 fi
+releasedir="$branch/releases/$arch"
 
 [ -n "$arch" ] || arch=$(apk --print-arch)