+Show changes between two ents, an ent and the working tree, an
+ent and the index file, or the index file and the working tree.
+The combination of what is compared with what is determined by
+the number of ents given to the command.
+
+`----------------`--------`-----------------------------`------------------
+Number of ents Options What's Compared Underlying command
+---------------------------------------------------------------------------
+0 - index file and working tree git-diff-files
+1 --cached ent and index file git-diff-index
+1 - ent and working tree git-diff-index
+2 - two ents git-diff-tree
+---------------------------------------------------------------------------