The Dockerfile language has some very frustrating limitations.
One I've found frequently frustrating is the inability to do any sort of globbing on COPY commands. This can make it very difficult to do some types of layer optimizations. For example in the Java world I have multi-project Gradle builds which consist of a tree of directories each of which contain a "build.gradle" file. I would like to copy all of these files, preserving the directory structure, into the container so that I can run a preliminary "gradle assemble" command which installs third-party dependencies, then only after that copy the remaining contents of these directories. That way I only need to re-download dependencies if any of the "build.gradle" files change when building the container.
This turns out to be impossible to do in the Dockerfile language without manually listing out every "build.gradle" file in the directory tree.
One I've found frequently frustrating is the inability to do any sort of globbing on COPY commands. This can make it very difficult to do some types of layer optimizations. For example in the Java world I have multi-project Gradle builds which consist of a tree of directories each of which contain a "build.gradle" file. I would like to copy all of these files, preserving the directory structure, into the container so that I can run a preliminary "gradle assemble" command which installs third-party dependencies, then only after that copy the remaining contents of these directories. That way I only need to re-download dependencies if any of the "build.gradle" files change when building the container.
This turns out to be impossible to do in the Dockerfile language without manually listing out every "build.gradle" file in the directory tree.