core/cli: add --debug flag, add HPI_LOGS to docs

doc/SETUP.org

@@ -191,6 +191,8 @@ HPI comes with a command line tool that can help you detect potential issues. Ru
 
 If you only have a few modules set up, lots of them will error for you, which is expected, so check the ones you expect to work.
 
+If you're having issues with ~cachew~ or want to show logs to troubleshoot what may be happening, you can pass the debug flag (e.g., ~hpi --debug doctor my.module_name~) or set the ~HPI_LOGS~ environment variable (e.g., ~HPI_LOGS=debug hpi query my.module_name~) to print all logs, including the ~cachew~ dependencies. ~HPI_LOGS~ could also be used to silence ~info~ logs, like ~HPI_LOGS=warning hpi ...~
+
 If you have any ideas on how to improve it, please let me know!
 
 Here's a screenshot how it looks when everything is mostly good: [[https://user-images.githubusercontent.com/291333/82806066-f7dfe400-9e7c-11ea-8763-b3bee8ada308.png][link]].

my/core/__main__.py

@@ -486,13 +486,18 @@ def query_hpi_functions(
 
 
 @click.group()
-def main() -> None:
+@click.option("--debug", is_flag=True, default=False, help="Show debug logs")
+def main(debug: bool) -> None:
     '''
     Human Programming Interface
 
     Tool for HPI
     Work in progress, will be used for config management, troubleshooting & introspection
     '''
+    # should overwrite anything else in HPI_LOGS
+    if debug:
+        os.environ["HPI_LOGS"] = "debug"
+
     # for potential future reference, if shared state needs to be added to groups
     # https://click.palletsprojects.com/en/7.x/commands/#group-invocation-without-command
     # https://click.palletsprojects.com/en/7.x/commands/#multi-command-chaining