abuild: rootbld: reflect build branch in the builder hostname

abuild.in

@@ -2078,6 +2078,12 @@ rootbld() {
 	cp /etc/abuild.conf /etc/group /etc/passwd "$BUILD_ROOT/etc"
 	cp /etc/apk/keys/* "$BUILD_ROOT/etc/apk/keys"
 
+	local version="edge" buildhost="edge" gitref
+	if gitref="$(expr "$(git symbolic-ref --short HEAD)" : '\([0-9]\+\(\.[0-9]\+\)*\)-')"; then
+		version=v${gitref}
+		buildhost=${gitref/./-}
+	fi
+
 	local repo_template=$aportsgit/$repo/.rootbld-repositories
 	[ -s "$repo_template" ] || die "rootbld: $repo_template does not exist"
 	(
@@ -2090,14 +2096,6 @@ rootbld() {
 		export mirror version
 		[ "$mirror" ] || mirror=http://dl-cdn.alpinelinux.org/alpine
 
-		if [ -z "$version" ]; then
-			version=$(git symbolic-ref --short HEAD)
-			[ "$version" ] && \
-				version=$(expr "$version" : '\([0-9]\+\(\.[0-9]\+\)*\)-') && \
-				version=v${version}
-			[ "$version" ] || version=edge
-		fi
-
 		envsubst
 		echo "$REPODEST/$repo"
 	) < "$repo_template" > "$BUILD_ROOT/etc/apk/repositories"
@@ -2119,7 +2117,7 @@ rootbld() {
 		--bind "$BUILD_ROOT/tmp/pkg" "$pkgbasedir" \
 		--bind "$BUILD_ROOT/tmp" /tmp \
 		--bind "$REPODEST" "$REPODEST" \
-		--hostname "build-edge-$CARCH" \
+		--hostname "build-$buildhost-$CARCH" \
 		--chdir "$startdir" \
 		--setenv PATH /bin:/usr/bin:/sbin:/usr/sbin \
 		/usr/bin/abuild $force rootbld_actions