How to pull changes from Developer Org when using Salesforce DX CLI

Winter 19 release has pilot commands to help with non scratch orgs.

You will need sfdx client pre release plugin installed to try .

The commands are

sfdx force:source:retrieve -- retrieves metadata from the org using package.xml or metadata folder or comma separated list of metadata 

sfdx force:source:deploy -- deploy metadata to the non scratch org

To get started follow the instructions here

Install the Pre-Release Version of the CLI

sfdx plugins:install salesforcedx@pre-release

Make sure that you have the pre-release version.

sfdx plugins --core

salesforcedx 44.0.1-xx

When the plugin is officially released v44 in mid October 2018, uninstall the pre-release version, then run the update command.

sfdx plugins:uninstall salesforcedx

sfdx update

force:source:pull is used to pull from scratch org only.

To 'pull' from developer org you need to use metadata API.

Use the force:mdapi:retrieve command.

For more info:

• https://developer.salesforce.com/docs/atlas.en-us.sfdx_cli_reference.meta/sfdx_cli_reference/cli_reference_force_mdapi.htm