-LONG_USAGE='If <branch> is specified, switch to that branch first. Then,
-extract commits in the current branch that are not in <upstream>,
-and reconstruct the current on top of <upstream>, discarding the original
-development history. If --onto <newbase> is specified, the history is
-reconstructed on top of <newbase>, instead of <upstream>. For example,
-while on "topic" branch:
+LONG_USAGE='git-rebase applies to <upstream> (or optionally to <newbase>) commits
+from <branch> that do not appear in <upstream>. When <branch> is not
+specified it defaults to the current branch (HEAD).
+
+When git-rebase is complete, <branch> will be updated to point to the
+newly created line of commit objects, so the previous line will not be
+accessible unless there are other references to it already.
+
+Assuming the following history: