Just in case if you are doing something exotic, it should be
noted that all of the <commit> in the above description, except
-for the last two forms that use ".." notations, can be any
-<tree-ish>.
+in the last two forms that use ".." notations, can be any
+<tree>. The third form ('git diff <commit> <commit>') can also
+be used to compare two <blob> objects.
For a more complete list of ways to spell <commit>, see
"SPECIFYING REVISIONS" section in linkgit:gitrevisions[7].