fix: Use ${BASH_SOURCE[0]} instead of $0 to link scripts

[quilicicf]

Summary

While trying to run asdf in a Jenkins kubernetes agent, we noticed the following error:

/home/jenkins/.asdf/bin/asdf: line 5: ./lib/utils.bash: No such file or directory
/home/jenkins/.asdf/bin/asdf: line 28: asdf_dir: command not found
/home/jenkins/.asdf/bin/asdf: line 81: asdf_dir: command not found
Unknown command: `asdf current`

We noticed that this stems from using dirname "$0" to find the path to the current script.

Depending on the context in which the script is run, $0 seems to return different values.

Changing all occurrences by ${BASH_SOURCE[0]} or directly using ${ASDF_DIR} seems to fix this.

You can reproduce this by:

• creating the Dockerfile below

  FROM ubuntu
  
  RUN apt update \
    && apt install git -y \
    && git clone https://github.com/asdf-vm/asdf.git ~/.asdf
  
  ENV BASH_ENV=/root/.asdf/asdf.sh
  

• building the Docker image like with:

  docker buildx build --tag asdf .
  

• run the following command:

  docker run -it --rm "$IMAGE" bash asdf current
  

Test the fix

I tested the fix by following the same instructions with the Docker image created from my code by putting the following Dockerfile in the repository:

FROM ubuntu

COPY . /root/.asdf

RUN apt update && apt install git -y

ENV BASH_ENV=/root/.asdf/asdf.sh

This was not a full test though.