[Perl hackers] A notional token passed around among the members of a project. Possession of the patch pumpkin means one has the exclusive authority to make changes on the project's master source tree. The implicit assumption is that pumpkin holder status is temporary and rotates periodically among senior project members.
This term comes from the Perl development community, but has been sighted elsewhere. It derives from a stuffed-toy pumpkin that was passed around at a development shop years ago as the access control for a shared backup-tape drive.