Implement clears in addMutations

include/VersionedMap.h

@@ -31,7 +31,7 @@ namespace weaselab {
  *
  * Thread safety:
  *   - It's safe to operate on two different VersionedMaps in two different
- * threads concurrently
+ * threads concurrently.
  *   - It's safe to have multiple threads operating on the same VersionedMap
  * concurrently if all threads only call const methods.
  *   - Methods that make stronger guarantees about the safety of calling
@@ -51,7 +51,7 @@ struct VersionedMap {
     Clear,
   };
 
-  /** bytes ordered bitwise-lexicographically. */
+  /** Bytes ordered bitwise-lexicographically. */
   struct Key {
     const uint8_t *p;
     int len;
@@ -86,12 +86,15 @@ struct VersionedMap {
   /** The version of the most recent call to `setOldestVersion`. */
   int64_t getOldestVersion() const;
 
-  /** Iterates through a canonicalized view of all the mutations from
-   * `oldestVersion` to the iterator's version. There may be mutations from
+  /** Iterates through a partially canonicalized[1] 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. 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`. */
+   * @warning must not outlive its `VersionedMap`.
+   *
+   * [1]: Mutations are sorted and non-overlapping, but may be adjacent.
+   */
   struct Iterator {
 
     Iterator() = default;