update docs with example for local-only usage

[sam-goodwin]

I am trying to run the getting started command within my repo. I don't want to pull from git, I just want to build the image from my local file system with a locally cloned repository.

Have tried this:

docker run -it --rm \
  -v /tmp/envbuilder:/workspaces \
  -e DEVCONTAINER_DIR=.devcontainer \
  -e DEVCONTAINER_JSON_PATH=.devcontainer/devcontainer.json \
  ghcr.io/coder/envbuilder

No matter what I do, I get this error:

error: no Dockerfile or devcontainer.json found: no fallback image has been specified
error: no Dockerfile or devcontainer.json found: no fallback image has been specified

From the docs, it is not clear how to use this tool from a local git repository. It always assumes a hosted repo which is not what I am trying to do.

[sam-goodwin]

Think I've found a workaround with a custom Dockerfile

FROM ghcr.io/coder/envbuilder

ENV WORKSPACE_FOLDER /workspaces

COPY .devcontainer /workspaces/.devcontainer

[sam-goodwin]

I genuinely have no idea how to use this tool without having a public Git repository and using GIT_URL which is meant to be optional. I think the docs could use some more examples.

[johnstcn]

The simplest way I've found to do this is to simply mount the repository to /workspaces/empty.

[johnstcn]

Fixed in #342