av stack reorder it's too easy to get into a bad state and loose commits

[Brookke]

Reproduction

1. Create a branch with several commits

   av stack branch demo
   git commit -m "feature a" --allow-empty
   git commit -m "feature b" --allow-empty
   git commit -m "feature c" --allow-empty
   

2. run av stack reorder

3. edit the file to:

   stack-branch demo --trunk master@b91a233a59c7f8a92ab3ef721237b463cebddb86
   pick 5399908  # feature a
   stack-branch feature/b # note I have forgotten the --parent flag here
   pick 0eb9dbf  # feature b
   stack-branch feature/c # note I have forgotten the --parent here
   pick 89b8117  # feature c
   

4. save and exit

Result

The command correctly errors. However, the feature b and feature c commits are now lost.

$ av stack reorder 
Starting branch demo at b91a233
  - applied commit 5399908 without conflict (HEAD is now at 5399908)
error: invalid stack-branch command: --parent=<branch> or --trunk=<branch> must be specified when creating the first branch

Expected result

because the command errors it should revert back to the prior state

Additional notes

Some of this could also be alleviated with a av stack split command that cut up a branch into a branch per commit (use the commit name as the branch name)

[draftcode]

Aside from this, we can save something similar to reflog so that we can record the ref updates as a safety. Save something like:

{
  operations: [
    {
      command: "av stack sync",
      refUpdates: [
        {
          ref: "refs/heads/feature1",
          before: "b91a233a59c7f8a92ab3ef721237b463cebddb86",
          after: "0000000000000000000000000000000000000000",
        }
      ]
    }
  ]
}

Technically, similar data should be stored in reflog, but a bit more explicit in terms of what we've done.