fix(site) Dont remove files from gh-pages

[montogeek]

I manually tweaked our site source code (https://github.com/webpack/webpack.js.org/tree/feat/v3-docs) to generate a build that runs in a subfolder for webpack 3 docs, which I deployed to https://webpack.js.org/v3/ using gh-pages branch.

There is a daily cronjob that updates gh-pages branch with latest changes from master, it also deletes current files from that branch, which deletes previous v3 build.

This PR adds a flag to gh-pages dependency to save previous files, I am afraid that it will also increment size of the branch, but I think it won't affect website performance.

This is a temporary solution until we develop a solution to support versioned docs, as lodash.com, hopefully this will be done in less than a month.

[jeremenichelli]

I don't know if this might endanger some other aspects of the deployment like when a file name changes or a route gets deleted in the future.

Does the build job brings all the content from the v3 tag and deploys it in the subdirectory folder? SO this would mean that in the future we can just delete the folder and remove this option and kill the subdirectory files.

[montogeek]

Does the build job brings all the content from the v3 tag and deploys it in the subdirectory folder?

No

[montogeek]

This is not going to work, we will need to build it like you say, which is a wasting of time since it will never change

[montogeek]

Not a solution.