Webpack ts-loader : change tsconfig filename

Question

I have 2 tsconfigs, one for my dev build and one for my prod build.
I choose the tsconfig with the -p flag :
tsc -p dev.tsconfig.json

Ts-loader is looking for a tsconfig.json file. How can I specify another filename with the ts-loader?

module.exports = {
    entry : __dirname + "/src/app/main.ts",
    output : {
        path : __dirname + "/dist",
        filename : "bundle.js"
    },
   resolve : {
     extensions : ["", ".webpack.js", ".web.js", ".js", ".ts"]
   },
   module: {
        loaders: [
            { test: /\.ts?$/, loader: "ts" }
        ]
    }
};

Answer 1

Update (Webpack 4): As noted in the comments, the syntax has changed as referenced in the answer below.

---

Webpack enables us to add custom options for each loader. All ts-loader configuration properties are described here.

configFileName is the property you are looking for. It should be like this.

module.exports = {
    entry : __dirname + "/src/app/main.ts",
    output : {
        path : __dirname + "/dist",
        filename : "bundle.js"
    },
    resolve : {
        extensions : ["", ".webpack.js", ".web.js", ".js", ".ts"]
    },
    module: {
        loaders: [
            { test: /\.ts?$/, loader: "ts" }
        ]
    },
    ts: {
        configFileName : 'dev.tsconfig.json'
    }
};