Prepare to fully canonicalize views

include/VersionedMap.h

@@ -86,16 +86,13 @@ struct __attribute__((__visibility__("default"))) VersionedMap {
   /** The version of the most recent call to `setOldestVersion`. */
   int64_t getOldestVersion() const;
 
-  /** Iterates through a canonicalized[1] view of all the mutations
+  /** Iterates through a canonicalized view of all the mutations
    * from `oldestVersion` to the iterator's version. There may be mutations from
    * versions < `oldestVersion`, but they won't affect the result, and can be
    * ignored if desired. It's thread-safe to operate on an iterator concurrently
    * with any method of `VersionedMap`, as long as it's not invalidated by
    * `setOldestVersion`.
    * @warning must not outlive its `VersionedMap`.
-   *
-   * [1]: Clears at different versions may be adjacent. This is necessary for
-   * precisely tracking at what version the mutations take effect.
    */
   struct Iterator {
 
@@ -114,7 +111,10 @@ struct __attribute__((__visibility__("default"))) VersionedMap {
       int param1Len;
       int param2Len;
       MutationType type;
-      int64_t version;
+      /** The set of keys modified by this mutation have not been modified since
+       * this version. They were not necessarily modified at this version
+       * though. */
+      int64_t notModifiedSince;
     };
 
     /** iter must not be `end()`. Memory pointed-to by return value is valid as