So, I have a dummy project, which file structure looks like this:
docker-magic
├── Dockerfile
├── .dockerignore
├── just_a_file
├── src
│ ├── folder_one
│ │ ├── main.go
│ │ └── what_again.sh
│ ├── folder_two
│ │ └── what.kts
│ └── level_one.go
└── top_level.go
My Dockerfile looks like this:
FROM ubuntu:latest as builder
WORKDIR /workdir
COPY ./ ./
RUN find . -type f
ENTRYPOINT ["echo", "wow"]
I build this image with a docker build . -t docker-magic:test --no-cache command to avoid caching results.
The idea is simple - I copy all of the files from docker-magic folder into my image and then list all of them via find . -type f.
Also I want to ignore some of the files. I do that with a .dockerignore file. According to the official Docker docs:
The placement of ! exception rules influences the behavior: the last line of the .dockerignore that matches a particular file determines whether it is included or excluded.
Let's consider following contents of .dockerignore:
**/*.go
It should exclude all the .go files. And it does! I get following contents from find:
./.dockerignore
./src/folder_one/what_again.sh
./src/folder_two/what.kts
./just_a_file
./Dockerfile
Next, let's ignore everything. .dockerignore is now:
**/*
And, as expected, I get empty output from find.
Now it gets difficult. I want to ignore all the files except .go files. According to the docs, it would be the following:
**/*
!**/*.go
But I get the following output from find:
./top_level.go
Which is obviously not what is expected, because other .go files, as we have seen, also match this pattern. How do I get the result I wanted - copying only .go files to my image?
EDIT: my Docker version is 20.10.5, build 55c4c88.