How can I append a line to a git commit message from the command line?

Question

I'd like to append (leaving the rest of the commit message intact) a line to my last commit from the command line (ie without having to open my editor). Is there anyway to do this?

Answer 1

Example commit:

git commit -m 'foo'
#foo 

Appending the string bar :

git commit --amend -m "$(git log --format=%B -n 1) bar"
#foo bar