Merge branch 'jk/maint-avoid-streaming-filtered-contents' into maint

* jk/maint-avoid-streaming-filtered-contents:
  do not stream large files to pack when filters are in use
  teach dry-run convert_to_git not to require a src buffer
  teach convert_to_git a "dry run" mode

diff --cc convert.c
Simple merge

diff --cc sha1_file.c
Simple merge