irmin-pack: add an explicit default value for indexing strategy

src/irmin-pack/conf.ml

@@ -29,7 +29,7 @@ module Default = struct
   let readonly = false
   let merge_throttle = `Block_writes
   let freeze_throttle = `Block_writes
-  let indexing_strategy = Pack_store.Indexing_strategy.always
+  let indexing_strategy = Pack_store.Indexing_strategy.default
 end
 
 open Irmin.Backend.Conf

src/irmin-pack/irmin_pack_intf.ml

@@ -48,7 +48,10 @@ module type Sigs = sig
         the strategy to use when the index cache is full and an async
         [Index.merge] in already in progress. [Block_writes] (the default)
         blocks any new writes until the merge is completed. [Overcommit_memory]
-        does not block but indefinitely expands the in-memory cache. *)
+        does not block but indefinitely expands the in-memory cache.
+      @param indexing_strategy
+        The {{!Pack_store.Indexing_strategy} indexing strategy} of the backend
+        store. Defaults to {!Pack_store.Indexing_strategy.default}. *)
 
   exception RO_not_allowed
 

src/irmin-pack/pack_store.ml

@@ -26,6 +26,8 @@ module Indexing_strategy = struct
            indexed (as they may be referenced via hash by other V0 objects), and
            this must be accounted for when reconstructing the index. *)
         true
+
+  let default = always
 end
 
 module type S = S with type indexing_strategy := Indexing_strategy.t

src/irmin-pack/pack_store_intf.ml

@@ -76,6 +76,11 @@ module type Sigs = sig
     val minimal : t
     (** The strategy that indexes as few objects as possible while still
         maintaing store integrity. *)
+
+    val default : t
+    (** [default] is the indexing strategy used by [irmin-pack] instances that
+        do not explicitly set an indexing strategy in {!Irmin_pack.config}.
+        Currently set to {!always}. *)
   end
 
   module type S = S with type indexing_strategy := Indexing_strategy.t