Avoid COPY . . in Dockerfile

TL;DR

Use COPY src src.

Security Consideration

Refer to the Sysdig's post.

COPY . . will place credentials in container by default. You will need to configure .dockerignore to avoid this. However, managing .dockerignore is tedious and easy to make mistake. This is just like .gitignore.

Whitelist copying like COPY src src and copy build build never cause this problem.

Layer efficiency

The files required by a command are different by step. For example, npm install requires only package.json and package-lock.json. Overwriting them in a later step by COPY . . may cause a consistency problem. In addition, not the builder container but only the runner container requires the files under src in Node.js, Ruby, Python, and so on with builder pattern.

Conclusion

I suggest to use whitelist copying to avoid some security problems. Build time will become shorter as a bonus.