Merge branches 'jc/convert', 'jc/bigfile' and 'jc/replacing' into jc/streaming

Merge branches 'jc/convert', 'jc/bigfile' and 'jc/replacing' into jc/streaming

* jc/convert:
  convert: make it harder to screw up adding a conversion attribute
  convert: make it safer to add conversion attributes
  convert: give saner names to crlf/eol variables, types and functions
  convert: rename the "eol" global variable to "core_eol"

* jc/bigfile:
  Bigfile: teach "git add" to send a large file straight to a pack
  index_fd(): split into two helper functions
  index_fd(): turn write_object and format_check arguments into one flag

* jc/replacing:
  read_sha1_file(): allow selective bypassing of replacement mechanism
  inline lookup_replace_object() calls
  read_sha1_file(): get rid of read_sha1_file_repl() madness
  t6050: make sure we test not just commit replacement
  Declare lookup_replace_object() in cache.h, not in commit.h