Replace old message when generating a new one

[jdgirald]

if I stage a file and generate a commit message and then stage a second file and click the button again, the file gets repeated in the commit message

e.g.:
fist message: feat: create compare_nodes.js
second message: feat: create package2.xml and compare_nodes.js create compare_nodes.js

[MichaelCurrin]

This behavior is intentional so you can start with a prefix like feat: and have the rest filled after it without losing the first part.

I need to figure how if I can make this smarter to avoid the situation you had, or to make a toggle in preferences.