[Bug]: `container build` not using `context-dir`

[0xEDU]

I have done the following

• I have searched the existing issues
• If possible, I've reproduced the issue using the 'main' branch of this project

Steps to reproduce

1. Run build with any other path: container build ..
2. If there's Dockerfile in the current path, it will build it. If there's not a Dockerfile, it will throw:
   Error: Dockerfile does not exist at path: Dockerfile

Current behavior

The build command does ignores the context-dir passed to it, it builds the Dockerfile it finds at the current path or throw an error if there is none.

Expected behavior

build should use the argument path as the context directory instead of always using the current path.

Environment

- OS: 26.0.1
- Xcode: 26.0.1 (25A362)
- Container: container CLI version 0.5.0

Relevant log output

Error: Dockerfile does not exist at path: Dockerfile
Usage: container build [<options>] [<context-dir>]
  See 'container build --help' for more information.

Code of Conduct

• I agree to follow this project's Code of Conduct

[mdempsky]

I believe context-dir does work. E.g., it's used for resolving COPY file paths.

But container build path/to/dir acts like container build -f ./Dockerfile path/to/dir, whereas docker build path/to/dir acts like docker build -f path/to/dir/Dockerfile path/to/dir.

Probably container build should act like docker build when the -f flag is not provided.

[0xEDU]

But container build path/to/dir acts like container build -f ./Dockerfile path/to/dir, whereas docker build path/to/dir acts like docker build -f path/to/dir/Dockerfile path/to/dir.

Exactly as @mdempsky described. I was able to reproduce the expected behavior using container build -f ../Dockerfile ... I do agree that it should behave like Docker in this situation, my intuition as a user is that it would try to use the Dockerfile in the context-dir.

[0xEDU]

I've opened PR #793 proposing a solution to this, feedback appreciated!