Add a way to specify a default group max per row

Author: dstein64

doc/scrollview.txt

@@ -390,8 +390,9 @@ scrollview_signs_max_per_row_by_group      *scrollview_signs_max_per_row_by_grou
                        |Dictionary| mapping sign groups (|String|) to maximum
                        number of corresponding signs per row (|Number|). Groups
                        not present in the dictionary, or that have a value of
-                       `-1`, have no group-specific limit. Defaults to `{}`.
-                       Example: `{'diagnostics': 1, 'keywords': 2}`.
+                       `-1`, have no group-specific limit. Use `'all'` to set a
+                       default limit for groups not explicitly specified.
+                       Defaults to `{}`. Example: `{'all': 2, 'diagnostics': 1}`.
 
 scrollview_signs_on_startup                *scrollview_signs_on_startup*
                        |List| of |String|s specifying built-in sign groups to

lua/scrollview.lua

@@ -1875,7 +1875,9 @@ local show_signs = function(winid, sign_winids, bar_winid)
       local filtered_list = {}
       for _, props in ipairs(props_list) do
         local group = sign_specs[props.sign_spec_id].group
-        local group_limit = max_signs_per_row_by_group[group] or -1
+        local group_limit = max_signs_per_row_by_group[group]
+          or max_signs_per_row_by_group['all']
+          or -1
         group_counts[group] = (group_counts[group] or 0) + 1
         if group_limit < 0 or group_counts[group] <= group_limit then
           table.insert(filtered_list, props)