rule: add global default_branch_filters

If prefix rule has local `branch_filters` defined, use that.
Otherwise, use `default_branch_filters` (if defined).

Author: yasunariw

lib/action.ml

@@ -16,13 +16,15 @@ module Action (Github_api : Api.Github) (Slack_api : Api.Slack) = struct
     let default = Option.to_list cfg.prefix_rules.default_channel in
     let rules = cfg.prefix_rules.rules in
     let branch = Github.commits_branch_of_ref n.ref in
+    let default_branch_filters = cfg.prefix_rules.default_branch_filters in
+    let filter_by_branch = Rule.Prefix.filter_by_branch ~branch ~default_branch_filters in
     n.commits
     |> List.filter ~f:(fun c ->
          let skip = Github.is_main_merge_message ~msg:c.message ~branch cfg in
          if skip then log#info "main branch merge, ignoring %s: %s" c.id (first_line c.message);
          not skip)
     |> List.concat_map ~f:(fun commit ->
-         let rules = List.filter ~f:(Rule.Prefix.filter_by_branch ~branch ~distinct:commit.distinct) rules in
+         let rules = List.filter ~f:(filter_by_branch ~distinct:commit.distinct) rules in
          let matched_channel_names =
            Github.modified_files_of_commit commit
            |> List.filter_map ~f:(Rule.Prefix.match_rules ~rules)

lib/config.atd

@@ -12,6 +12,7 @@ type status_rules = {
   files they are related to. *)
 type prefix_rules = {
   ?default_channel: string nullable; (* if none of the rules is matching *)
+  ~default_branch_filters <ocaml default="[]">: string list;
   rules: prefix_rule list;
 }
 

lib/rule.ml

@@ -39,11 +39,16 @@ module Status = struct
 end
 
 module Prefix = struct
-  (** Filters prefix rules based on config and current commit. Returns true if
-      `branch_filters` includes the commit branch, or if it's empty but the
-      commit is `distinct`. *)
-  let filter_by_branch ~branch ~distinct rule =
-    (List.is_empty rule.branch_filters && distinct) || List.mem rule.branch_filters branch ~equal:String.equal
+  (** Filters prefix rules based on branch filtering config and current commit.
+      Prioritizes local filters over default ones. Only allows distinct commits
+      if no filter is matched. *)
+  let filter_by_branch ~branch ~default_branch_filters ~distinct rule =
+    match rule.branch_filters with
+    | _ :: _ as filters -> List.mem filters branch ~equal:String.equal
+    | [] ->
+    match default_branch_filters with
+    | _ :: _ as filters -> List.mem filters branch ~equal:String.equal
+    | [] -> distinct
 
   (** `match_rules f rs` returns the channel name of a rule in `rs` that matches
       file name `f` with the longest prefix, if one exists. A rule `r` matches