rebase: change "editform" to distinguish merge commits from others "editform" argument for "getcommiteditor" is decided according to the format below: EXTENSION[.COMMAND][.ROUTE] - EXTENSION: name of extension - COMMAND: name of command, if there are two or more commands in EXTENSION - ROUTE: name of route, if there are two or more routes in COMMAND This patch newly adds "merge" as ROUTE, to distinguish merge commits from other. This patch passes bool as "ctxorbool" to "mergeeditform", because working context has always 2 parents at this point. Dropping the second parent of non-merging commits is executed in "concludenode". Unlike other patches in this series (e.g. for "hg commit"), this patch doesn't add "normal.normal"/"normal.merge" style ROUTEs, because there is no "merge" case in "collapse" ROUTE.