This rule enforces that when the COPY instruction in a Dockerfile has more than two arguments, the last argument must be a directory path ending with a slash (/). This ensures that multiple source files or directories are copied into the specified destination directory correctly. Always ensure that when copying multiple files or directories, the destination path ends with a slash, clearly indicating it is a directory. For example, use COPY package.json yarn.lock my_app/ instead of COPY package.json yarn.lock my_app. This practice improves clarity and prevents ambiguous or incorrect Docker image builds.
