Append messages instead of replacing the commit message

[Pierstoval]

Hi, I just discovered this tool and it's absolutely awesome ! Now I can squash tons of my commits in a single one, and it's great :+1:

I was wondering about adding a new feature:

Add a --append-message|-a argument that will save all commit logs messages in a var, and write them after squashing the commits.

I mean, here is an example:

* E - master
| 
* D - This one is great
| 
* C - This one too
| 
* B - That one was very crappy
| 
* A - This is the root commit

When running something like git squash C -m "Merged features" --append-message the commit message result will be the following:

Merged features
E - master
D - This one is great
C - This one too

Do you think it's possible ?