Comment by lambdafu

Yes, I should document that. GPGME only exposes a high-level API, and application developers often want more control. For example, you can't inspect key material before importing it, but importing a key is not a reversible operation - so applications sometimes use a temporary HOMEDIR for GPGME/GnuPG to import the key there and inspect it with a keylisting. It can be very cumbersome.