// The preceding configuration gives me the correct useminPrepare output:

// Running "useminPrepare:html" (useminPrepare) task
// Going through app/index.html to update the config
// Looking for build script HTML comment blocks

// Configuration is now:
{
    concat: {
        files: {
            '.tmp/concat/scripts/head-scripts.js': [
                'app/scripts/vendor/modernizr.js'
            ],
            '.tmp/concat/scripts/app-prod.js': [
                'app/scripts/main.js',
                'app/scripts/app.js'
            ]
        },
        generated: {
            files: [
                {
                    dest: '.tmp/concat/scripts/head-scripts.js',
                    src: [
                        'app/scripts/vendor/modernizr.js'
                    ]
                },
                {
                    dest: '.tmp/concat/scripts/app-prod.js',
                    src: [
                        'app/scripts/main.js',
                        'app/scripts/app.js'
                    ]
                }
            ]
        }
    }
    uglify: {
        files: {
            '<%= config.dist %>/concat/scripts/head-scripts.js': [
                '.tmp/concat/scripts/head-scripts.js'
            ],
            '<%= config.dist %>/concat/scripts/app-prod.js': [
                '.tmp/scripts/app-prod.js'
            ]
        },
        generated: {
            files: [
                {
                    dest: 'dist/scripts/head-scripts.js',
                    src: [
                        '.tmp/concat/scripts/head-scripts.js'
                    ]
                },
                {
                    dest: 'dist/scripts/app-prod.js',
                    src: [
                        '.tmp/concat/scripts/app-prod.js'
                    ]
                }
            ]
        }
    }
}