filemerge: use only the first line of the generated conflict marker for safety Before this patch, with careless configuration (missing '|firstline' filtering for '{desc}' keyword, for example), '[ui] mergemarkertemplate' can make conflict markers multiple lines. For ordinary users, advantage of allowing '[ui] mergemarkertemplate' to generate multiple lines for customizing seems to be less than advantage of disallowing it for safety. This patch uses only the first line of the conflict marker generated from '[ui] mergemarkertemplate' configuration for safety.