doc: git-rebase: start with an example

Start with an example that mirrors the example in the `git-merge` man
page, to make it easier for folks to understand the difference between a
rebase and a merge.

Signed-off-by: Julia Evans <[email protected]>

Author: jvns

Documentation/git-rebase.adoc

@@ -16,6 +16,26 @@ SYNOPSIS
 
 DESCRIPTION
 -----------
+Transplant a series of commits onto a different starting point.
+
+For example, assume the following history exists and the current branch is `topic`:
+
+------------
+          A---B---C topic
+         /
+    D---E---F---G master
+------------
+
+Then `git rebase master` will find all of the commits since `topic` diverged
+from `master` and copy the changes in each of those commits on top of the
+`master` branch.
+
+------------
+                  A'--B'--C' topic
+                 /
+    D---E---F---G master
+------------
+
 If `<branch>` is specified, `git rebase` will perform an automatic
 `git switch <branch>` before doing anything else.  Otherwise
 it remains on the current branch.
@@ -58,32 +78,6 @@ that caused the merge failure with `git rebase --skip`.  To check out the
 original `<branch>` and remove the `.git/rebase-apply` working files, use
 the command `git rebase --abort` instead.
 
-Assume the following history exists and the current branch is "topic":
-
-------------
-          A---B---C topic
-         /
-    D---E---F---G master
-------------
-
-From this point, the result of either of the following commands:
-
-
-    git rebase master
-    git rebase master topic
-
-would be:
-
-------------
-                  A'--B'--C' topic
-                 /
-    D---E---F---G master
-------------
-
-*NOTE:* The latter form is just a short-hand of `git checkout topic`
-followed by `git rebase master`. When rebase exits `topic` will
-remain the checked-out branch.
-
 If the upstream branch already contains a change you have made (e.g.,
 because you mailed a patch which was applied upstream), then that commit
 will be skipped and warnings will be issued (if the 'merge' backend is