Merge branch 'jc/fetch-pull-refmap'

* jc/fetch-pull-refmap: docs: Explain the purpose of fetch's and pull's <refspec> parameter. fetch: allow explicit --refmap to override configuration fetch doc: add a section on configured remote-tracking branches fetch doc: remove "short-cut" section fetch doc: update refspec format description fetch doc: on pulling multiple refspecs fetch doc: remove notes on outdated "mixed layout" fetch doc: update note on '+' in front of the refspec fetch doc: move FETCH_HEAD material lower and add an example fetch doc: update introductory part for clarity