Improve documentation regarding project outputs access from host

Signed-off-by: tdruez <tdruez@nexb.com>

Author: tdruez

docs/command-line-interface.rst

@@ -3,13 +3,24 @@
 Command Line Interface
 ======================
 
-A ``scanpipe`` command can be executed through the ``docker compose`` command line
-interface with::
+The ``scanpipe`` command can be executed using the Docker Compose command line interface.
+
+If the Docker Compose stack is already running, you can execute the command as follows:
+
+.. code-block:: shell
 
     docker compose exec -it web scanpipe COMMAND
 
-Alternatively, you can start a ``bash`` session in a new Docker container to execute
-multiple ``scanpipe`` commands::
+If the ScanCode.io services are not currently running, you can use the following command:
+
+.. code-block:: shell
+
+    docker compose run --rm web scanpipe COMMAND
+
+Additionally, you can start a new Docker container and execute multiple
+``scanpipe`` commands within a ``bash`` session:
+
+.. code-block:: shell
 
     docker compose run web bash
     scanpipe COMMAND
@@ -244,6 +255,8 @@ Optional arguments:
   compatible with the XLSX and CSV formats.
   It cannot be used when multiple formats are provided.
 
+Refer to :ref:`Mount projects workspace <mount_projects_workspace_volume>` to access
+your outputs on the host machine when running with Docker.
 
 `$ scanpipe archive-project --project PROJECT`
 ----------------------------------------------

docs/output-files.rst

@@ -30,6 +30,28 @@ the output file format with the ``–-format`` option:
     ``PROJECT``'s :guilabel:`output/` directory. By default, JSON output
     files are created when no file format is given.
 
+.. _mount_projects_workspace_volume:
+
+.. warning::
+    When running with Docker, ensure that the output files workspace is assigned
+    to a volume to be accessible on the host machine.
+
+    To add local input files to a project using the :ref:`command_line_interface`,
+    additional arguments need to be passed to the ``docker compose`` command.
+
+    For example, using the following command will mount and make available the
+    projects workspace on the host at ``~/projects/``:
+
+    .. code-block:: bash
+
+        mkdir ~/projects/
+        docker compose run --volume ~/projects/:/var/scancodeio/workspace/projects/ \
+            web scanpipe output --project my_project --format json
+
+    Alternatively, you can also locate the Docker volumes directory on your host
+    machine. For instance, on Linux, it's typically found at:
+    ``/var/lib/docker/volumes/``.
+
 Web UI
 ^^^^^^
 When using the ScanCode.io web application, you can download the results of your