a0963a1b51
This adds a setting for choosing which of {name, email, username} to use
as "author" when constructing the name for the branch to where a change
is downloaded.
The rationale is that sometimes the given "name" is just long and
unwieldy (when displaying the branch in the shell prompt, for example),
and one may be already used to the "username".
Change-Id: Ieed465f69ed0c0864979a92f609bd8f58cd8e883