In your daily tasks if you need to squash multiple commits into one with a custom message just perform the following commands:
git reset --soft HEAD~n # where n is the number of last commits you want to squash into one
git commit --amend
git push -f
another (interactive) way is to use rebase like below:
git rebase -i HEAD~n
the last n commit messages will appear in your text editor. You will see something similar to:
pick 0123456 Message 1
pick 1234567 Message 2
pick 2345678 Message 3
you could just pick the first commit and squash the rest like that:
p 0123456 Message 1
s 1234567 Message 2
s 2345678 Message 3