Should the `.aderc` file be necessary in the current directory?

I recently found out that you can use non-standardly named .aderc files by sourcing them. This results in certain environment variables being populated.

However, if you source such a file (i.e. .aderc-lgsvl), ade will still demand that it is run within a directory with a .aderc file, which doesn't seem exactly right.

IMO one or more of the following should be supported:

1. ade shouldn't complain about missing .aderc if the environment variables are already set
2. ade should provide a command line option to specify .aderc files to use
3. ade should probably also say which source it is getting the environment variables from (i.e. already set, or from a file)