Icon maximum length error during deployment

The error message is misleading.

The error was because the image file AllocationLogo.png was not present in Shared Documents.

Once I uploaded the file to shared documents, the deployment went through fine.

This is just a standard Metadata API deployment error so nothing specific to CircleCI or even really the Force.com Ant Migration Tool.

The documentation for CustomTab shows that the icon field is a reference to a document by ID which makes sense given the error that the field limit is 15: https://developer.salesforce.com/docs/atlas.en-us.api_meta.meta/api_meta/meta_tab.htm

To get the deploy to work, I think you'd have to know the document id of the icon which will be org specific.