Git trick for building docker images

git.docker.build

# source: https://github.com/docker/docker/issues/7198#issuecomment-200964423
As discussed above, when sharing content from your home folder into a container, add a user account with the same UID as yours. Here's a trick to cope if your UID isn't 1000. I assume that each user builds his own docker image from the Dockerfile.

Your Dockerfile should contain:

RUN useradd --uid 1000 -m vagrant
USER vagrant
The constant 1000 is substituted for your actual UID using a git filter. Run the following on your host:

git config filter.uidfix.smudge "sed s/1000/$UID/g"
git config filter.uidfix.clean "sed s/$UID/1000/g"
Finally, add a .gitattributes file to apply the git filter:

Dockerfile filter=uidfix
This works by replacing 1000 with your actual UID when you checkout the Dockerfile by smudging the file. Git will clean the file (putting back 1000) when you commit. Any commands run in the container run as vagrant user with the correct UID.