compact remake fixes base at the commit

Instead of fixing base heads at when proposed, compact fixes them when
committing.  This shrinks the window where writes can be lost if their
author restarts to the switch delay; during replace and import remakes
writes can still be lost during the voting period.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/remake/kind.rs b/src/remake/kind.rs
index 8131f7f..b36db4c 100644
--- a/src/remake/kind.rs
+++ b/src/remake/kind.rs
@@ -71,6 +71,14 @@ pub(crate) trait RemakeKind: Send + Sync + 'static {
 
     /// Every node: where a user path written after the base goes.
     fn translate(&self, path: &[String], translation: &JsonValue) -> Translation;
+
+    /// Whether the coordinator fixes the base when it commits instead of when it
+    /// proposes (no `baseHeads` then). Right for a kind whose content is the old
+    /// document at the base: the later the base, the fewer writes need carrying over,
+    /// and a write made after it is lost if its author restarts before switching.
+    fn base_at_commit(&self) -> bool {
+        false
+    }
 }
 
 /// The kind with this name.
@@ -97,6 +105,10 @@ impl RemakeKind for Compact {
         "compact"
     }
 
+    fn base_at_commit(&self) -> bool {
+        true
+    }
+
     fn propose(&self, spec: &JsonValue) -> Result<Prepared, String> {
         match spec {
             JsonValue::Null => Ok(Prepared::default()),