Support for !source syntax in .sql files

[sfc-gh-tjuch]

Description

SnowSQL offers the !source syntax to reference other SQL files. Docs: https://docs.snowflake.com/en/user-guide/snowsql-use#source-load. Having this feature in snowflake CLI would allow for streamlined management of SQL-based processes and parity with SnowSQL functionality.

Context

Currently, I use SnowSQL to manage installation of Snowflake assets (300+) at scale using an orchestrated tree process to run through SQL files. In order to easily transition from SnowSQL to Snowflake CLI, there would need to functionality to support calling one .sql from another. Calling multiple .sql files in a single snow sql -f statement would not scale.