feat: temporarily move rw mounts during image build

[johnstcn]

          This is an interesting question, should we or should we not limit this to read-only mounted filesystems? If we think about how a docker container is run with `-v /path:/path`, the contents of the docker container can never populate the mounted `/path`.

Originally posted by @mafredri in #183 (comment)

Currently, mounting in read-write volumes results in their contents not being available inside the container:

$ echo 'important stuff' >> /opt/important-stuff/tps-reports.txt
$ ls -l /opt/important-stuff/tps-reports.txt 
-rw-r--r-- 1 cian 16 May 13 21:12 /opt/important-stuff/tps-reports.txt
$ docker run -it --rm \
    -v /opt/important-stuff:/opt/important-stuff \
    -e GIT_URL=https://github.com/coder/envbuilder-starter-devcontainer \
    -e INIT_SCRIPT=bash \
    envbuilder:latest
[...]
devcontainer # ls -l /opt/important-stuff/
total 0
devcontainer # exit
$ cat /opt/important-stuff/tps-reports.txt
important stuff

Can we extend #183 to include all volumes mounted in?

[DanielleMaywood]

I'm unable to reproduce the behaviour mentioned.

Attempting to reproduce this on our dogfood instance

$ docker --version
Docker version 27.3.0, build e85edf8

$ ls /home/coder/casts
new-cliui-select      new-prompt-multiple      new-prompt-rich-parameter  new-roles-edit       no-blink               original-create-workspace  original-prompt-multi-select    original-prompt-select  original-template-delete
new-create-workspace  new-prompt-multi-select  new-prompt-select          new-template-delete  original-cliui-select  original-prompt-multiple   original-prompt-rich-parameter  original-roles-edit

$ docker run --rm -it \
    -v /home/coder/casts/:/opt/casts:rw \
    -e ENVBUILDER_GIT_URL=https://github.com/coder/envbuilder-starter-devcontainer \
    -e ENVBUILDER_INIT_SCRIPT=bash \
    envbuilder:latest

devcontainer # ls /opt/casts/
new-cliui-select      new-prompt-multi-select  new-prompt-rich-parameter  new-roles-edit       no-blink               original-create-workspace     original-prompt-multiple        original-prompt-select  original-template-delete
new-create-workspace  new-prompt-multiple      new-prompt-select          new-template-delete  original-cliui-select  original-prompt-multi-select  original-prompt-rich-parameter  original-roles-edit

devcontainer # exit

$ ls /home/coder/casts
new-cliui-select      new-prompt-multiple      new-prompt-rich-parameter  new-roles-edit       no-blink               original-create-workspace  original-prompt-multi-select    original-prompt-select  original-template-delete
new-create-workspace  new-prompt-multi-select  new-prompt-select          new-template-delete  original-cliui-select  original-prompt-multiple   original-prompt-rich-parameter  original-roles-edit

Attempting to reproduce this on a Ubuntu 24.04 VM

$ docker --version
Docker version 27.3.1, build ce12230

$ ls /tmp/important
a  b  c

$ docker run --rm -it \
    -v /tmp/important:/opt/important:rw \
    -e ENVBUILDER_GIT_URL=https://github.com/coder/envbuilder-starter-devcontainer \
    -e ENVBUILDER_INIT_SCRIPT=bash \
    ghcr.io/coder/envbuilder:latest

devcontainer # ls /opt/important/
a  b  c

devcontainer # exit

$ ls /tmp/important
a  b  c