Introduce `history_since_<id>` value expansion

The `history_since_<id>` value expansion allows incremental parsing of a
buffer's history.

    declare-option int my_last_history_id
    define-command my-process-history ...

    # process the initial buffer history
    my-process-history %val{bufname} 0 %val{history}
    set-option buffer my_last_history_id 0

    # only process new history changes on idle
    hook buffer NormalIdle %{
        evaluate-commands %exp{
            my-process-history \
                %%val{bufname} \
                %%opt{my_last_history_id} \
                %%val{history_since_%opt{my_last_history_id}}
        }
        set-option buffer my_last_history_id %val{history_id}
    }

1 files changed, 1 insertions, 1 deletions

diff --git a/src/buffer_utils.cc b/src/buffer_utils.cc
index a2d2e709..994dbd23 100644
--- a/src/buffer_utils.cc
+++ b/src/buffer_utils.cc
@@ -392,7 +392,7 @@ static String modification_as_string(const Buffer::Modification& modification)
                   modification.content->strview());
 }
 
-Vector<String> history_as_strings(const Vector<Buffer::HistoryNode>& history)
+Vector<String> history_as_strings(ConstArrayView<Buffer::HistoryNode> history)
 {
     Vector<String> res;
     for (auto& node : history)