Merge branch 'jt/keep-partial-clone-filter-upon-lazy-fetch'

The lazy fetching done internally to make missing objects available
in a partial clone incorrectly made permanent damage to the partial
clone filter in the repository, which has been corrected.

* jt/keep-partial-clone-filter-upon-lazy-fetch:
  fetch: do not override partial clone filter
  promisor-remote: remove unused variable

diff --cc builtin/fetch.c
Simple merge

diff --cc t/t5601-clone.sh
Simple merge