build: updates to Docker resources (#1696)

.gitattributes

@@ -0,0 +1 @@
+*.nix text eol=lf

.gitignore

@@ -6,6 +6,7 @@ aclocal.m4
 /autom4te.cache/
 Makefile
 .deps/
+.direnv
 config.h
 config.log
 config.status

Dockerfile

@@ -5,8 +5,7 @@ RUN echo "substituters = https://cache.nixos.org https://dissolve-nix.cachix.org
 RUN echo "trusted-public-keys = cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs= dissolve-nix.cachix.org-1:b7kp954+mmuowr7XZsAIBugv+xp7+n3aSF/5obidRDE=" >> /etc/nix/nix.conf
 RUN echo "experimental-features = nix-command flakes" >> /etc/nix/nix.conf
 RUN /root/.nix-profile/bin/nix build github:disorderedmaterials/dissolve#devShells.x86_64-linux.default
-RUN nix-env -iA nixpkgs.dos2unix
 VOLUME /dissolve
 WORKDIR /dissolve
 
-CMD [ "/bin/sh", "-c", "./scripts/setup.sh" ]
+CMD "/root/.nix-profile/bin/nix" "develop" "--extra-experimental-features" "nix-command" "--extra-experimental-features" "flakes" "/dissolve#"

web/docs/userguide/developers/docker.md

@@ -56,6 +56,21 @@ This will run a new instance of the built image in an interactive terminal - you
 
 Notice that this command maps the IP address of the host machine to the container (a requirement for X11 forwarding of graphics to take place) as well as mapping the dissolve code into the container. 
 
+Before starting any work, initialise the environment variables using `direnv`:
+```shell
+nix-env -iA nixpkgs.direnv
+direnv allow
+echo "$(direnv hook bash)" > /root/.bashrc
+```
+This will allow the environment to be reloaded automatically on future instances of starting the container (simply execute an interactive terminal with `bash` as the entrypoint - see step 4).
+
+To build the dissolve software using `cmake`, you will need to run the following commands
+```shell
+cmake --preset GUI-nix
+cmake --build build
+```
+The build products should now be visible in the `/build` directory on both the host and container file systems.
+
 To build the dissolve software using `cmake`, you will need to run the following commands
 ```shell
 cmake --preset GUI-nix
@@ -77,4 +92,11 @@ nixGLIntel ./build/bin/dissolve-gui
 ``` 
 to start the software.
 
-You should now see the dissolve home screen open in a new window.
+You should now see the dissolve home screen open in a new window.
+
+When the container is closed, the development shell with close, taking the environment dependencies with it.
+Therefore, any time returning to work inside the container, run  `docker start $CONTAINER_NAME`, and then
+```shell
+docker exec -it $CONTAINER_NAME sh -c "echo "$(direnv hook bash)" > /root/.bashrc; bash"
+```
+which will hook dissolve's dev environment into the new shell.