Merge branch 'fc/fetch-with-import-fix' into maint

Code restructuring during 2.20 period broke fetching tags via "import" based transports. * fc/fetch-with-import-fix: fetch: fix regression with transport helpers fetch: make the code more understandable fetch: trivial cleanup t5801 (remote-helpers): add test to fetch tags t5801 (remote-helpers): cleanup refspec stuff