For a command-line adventure using a script I've modified:

1. Visit https://github.com/DaveJarvis/github-email
1. Follow the [instructions](https://github.com/DaveJarvis/github-email#wget) to install into `$HOME/bin`.
1. Set your GitHub [token](https://github.com/DaveJarvis/github-email#authenication-token).
1. Open a new terminal.
1. Run: `github-email username`

The script automates using GitHub's HTTP REST API to find email addresses associated with Git commit histories. The script will also look for the user's contact information from a few different sources. You could perform all the steps the script takes from within a web browser.

The key line from the script is to retrieve all commits against a particular repository (owned by the user whose email address is desired):

``` bash
# Find all commits against the repository
$CMD -H "$PARAM_GITHUB_TOKEN" "$API_GITHUB/repos/$ARG_USERNAME/$ARG_REPOSITORY/commits" \
  | jq -r ".[] | .commit | .author | $NAME_FORMAT" 2>/dev/null \
  | sort \
  | uniq
```