That repository contains package source for OpenWRT SDK build system.
release folder contain sources for building package against tagged version of i2pd using release tarball and it's hash.
trunk folder contain sources with usage of git and commit hash used for building. To adjust build to latest commit update PKG_SOURCE_DATE and PKG_SOURCE_VERSION variables to your need. For example, values
PKG_SOURCE_DATE:=2021-12-25
PKG_SOURCE_VERSION:=1c95c7856f9a637f998882acaba679210bb9cb35
will use commit 1c95c78 and mark package version using date 2021-12-25, so resulting package name will like i2pd_2021-12-25-1c95c785-1_<arch>.ipk.