git config --unset does not remove section

Hello,

git config --unset does not remove the section in the configuration
file when the removed key is the last one, leaving then an empty
section that is lo longer used. E.g.:

    git config foo.bar true

creates:

    [foo]
	bar = true

then:

    git config --unset foo.bar

changes the section into:

    [foo]

Another git config foo.bar true changes the config file into:

    [foo]
    [foo]
	bar = true

Having two sections with the same name clutters the config file.

-Angelo Borsotti