[Request]: Improve hab --site cli

[MHendricks]

Description

The hab --site ... cli call is useful for testing and to ensure a user runs a command with your development setup, but it is a little cumbersome having to pass --site for each path to include, and often you just want to prepend an argument to HAB_PATHS.

Solution

Add the ability to:

• Specify multiple paths with a single --site call. hab --site "~/dev.json;~host.json" dump --type site
• An easy way to append/prepend to the HAB_PATHS env var. hab --site "~/prepend.json;$HAB_PATHS;~/append.json" dump --type site

Additional Context

No response

[MHendricks]

We could possibly add a hab cfg or hab site command that would provide a unified way to set the HAB_PATHS env variable. Currently, you have to use the correct command for the shell the user is using.

cmd: set "HAB_PATHS=.../pre.json;%HAB_PATHS%;.../post.json"
powershell: $env:{key} = ".../pre.json;%HAB_PATHS%;.../post.json"
bash windows: export HAB_PATHS=".../pre.json;$HAB_PATHS;.../post.json".
bash linux: export HAB_PATHS=".../pre.json:$HAB_PATHS:.../post.json"

The hab activate command is able to modify env vars of the current shell, so we should be able to make the hab site command modify the HAB_PATHS env var. This command could work for all shells(Note unc paths will still require adding leading \\ for bash on windows.)

hab site".../dev.json" HAB_PATHS ".../post.json"