+--aggressive::
+ Usually a three-way merge by `git-read-tree` resolves
+ the merge for really trivial cases and leaves other
+ cases unresolved in the index, so that Porcelains can
+ implement different merge policies. This flag makes the
+ command to resolve a few more cases internally:
++
+* when one side removes a path and the other side leaves the path
+ unmodified. The resolution is to remove that path.
+* when both sides remove a path. The resolution is to remove that path.
+* when both sides adds a path identically. The resolution
+ is to add that path.
+
+--prefix=<prefix>/::
+ Keep the current index contents, and read the contents
+ of named tree-ish under directory at `<prefix>`. The
+ original index file cannot have anything at the path
+ `<prefix>` itself, and have nothing in `<prefix>/`
+ directory. Note that the `<prefix>/` value must end
+ with a slash.
+
+