Merge branch 'upstream'

Merge branch 'upstream'

* upstream: (1173 commits)
  Update CHANGELOG with the release number
  filter: add docs for streaming filters
  iterator_walk: cast away constness for free
  filter::stream: free the filter sanely
  submodule: correctly delimit the keys to use for lookup
  submodule: add failing test for loading the wrong submodule
  submodule: completely remove reload_all
  Fix 8.3 filename tests failure when 8.3 is disabled
  Fix #3093 - remove declaration of unused function git_fetch__download_pack
  http: fixed leak when asking for credentials again
  index tests: add eol to avoid compiler warning
  checkout test: mark unused vars
  winhttp: remove unused var
  posix compat: include sys/stat.h for mingw
  diff: use size_t format
  fix memory leak in refspec.c on errors.
  checkout test: check getcwd return value
  clar: test chdir
  filter test: pass base type
  examples: clean up some warnings
  ...