common/changed_templates.sh: store merge-base in file

common/travis/changed_templates.sh

@@ -8,9 +8,11 @@ elif command -v git >/dev/null 2>&1; then
 	GIT_CMD=$(command -v git)
 fi
 
+printf '%s ' "$(git merge-base FETCH_HEAD HEAD)" HEAD  > /tmp/revisions
+
 /bin/echo -e '\x1b[32mChanged packages:\x1b[0m'
 $GIT_CMD diff-tree -r --no-renames --name-only --diff-filter=AM \
-	"$(git merge-base FETCH_HEAD HEAD)" HEAD \
+	$(cat /tmp/revisions) \
 	-- 'srcpkgs/*/template' |
 	cut -d/ -f 2 |
 	tee /tmp/templates |