docs: describe `git commit --fixup` equivalent
It's probably not obvious that `jj move` can be used for the `git
commit --fixup` usecase.
@@ -226,6 +226,11 @@ parent.
<td><code>jj squash/amend -i</code></td>
<td><code>git add -p; git commit --amend</code></td>
</tr>
+ <tr>
+ <td>Move the diff in the working copy into an ancestor</td>
+ <td><code>jj move --to X</code></td>
+ <td><code>git commit --fixup=X; git rebase -i --autosquash X^</code></td>
+ </tr>
<tr>
<td>Interactively move part of the diff in an arbitrary change to another
arbitrary change</td>
