Better user handling

[tschaub]

When the gh-pages command runs, it creates a repo in a cache directory. By default, this directory is in the gh-pages install directory (e.g. path/to/node_modules/gh-pages/.cache).

Previously, commits that were created in the cached repo used the git config user.email and git config user.name as determined from the cached repo. In the case of a global gh-pages install, this user name and email would most likely be the global git user. In the case of a local gh-pages install, this would be a local git user if one was configured.

This branch changes things so that the user is determined by running git config user.email (and same for name) in the current working directory. This means that the git user will be the local user if the current directory is a git repo and has a locally configured user. Otherwise it will be the global git user.

To override the behavior of determining the git user, a user option can be provided. For the CLI, the format of this option is "Full Name <email@example.com" (see RFC-5322). For example:

gh-pages -d dist --user "Your Name <you@example.com>"

The same behavior applies to programmatic usage. A {name, email} object can be provided for the user option. If not provided, git config user.email will be run in the current working directory.

Thanks to @holloway for initiating this in #229. And to @nuklearfiziks for resurrecting it once and @paulirish for resurrecting it a second time in #261.

[nuklearfiziks]

This is fantastic; thank you for fixing this!! 👏 🙌