Hi. I noticed that the position of the `--preserve-merges` option of
`git rebase` is significant (I think it shouldn't).
The following snippet doesn't preserve the merges:
```
$ git rebase --preserve-merges -i 412f07a~
pick 412f07a Work on dev branch
pick c6efccd Work on master branch
pick 71c8c37 Some work after the merge
```
Whereas this one does what I expect:
```
$ git rebase -i 412f07a~ --preserve-merges
pick 412f07a Work on dev branch
pick 616064c Merge branch 'master' into dev
pick 71c8c37 Some work after the merge
```
For reference:
```
$ git log --graph --oneline
* 71c8c37 (HEAD -> dev) Some work after the merge
* 616064c Merge branch 'master' into dev
|\
| * c6efccd Work on master branch
| * ... (more work on master)
* | 412f07a Work on dev branch
* | ... (more work on dev)
|/
* 4ee50cb Common ancestor
```
Step to reproduce:
```
mkdir temp
cd temp
git init
git commit --allow-empty -m 'Common ancestor'
git checkout -b dev
git commit --allow-empty -m 'Work on dev branch'
git tag some_commit
git checkout master
git commit --allow-empty -m 'Work on master branch'
git checkout dev
git merge master -m 'Merge branch 'master' into dev'
git commit --allow-empty -m 'Some work after the merge'
```
Then you will see that
git rebase -i some_commit --preserve-merges
and
git rebase --preserve-merges -i some_commit
don't have the same output.
I am using git version 2.21.1 on Fedora 30.
Robin.
