Merge branch 'np/fast-import-idx-v2' into maint

* np/fast-import-idx-v2:
  fast-import: use the diff_delta() max_delta_size argument
  fast-import: honor pack.indexversion and pack.packsizelimit config vars
  fast-import: make default pack size unlimited
  fast-import: use write_idx_file() instead of custom code
  fast-import: use sha1write() for pack data
  fast-import: start using struct pack_idx_entry

Documentation/git-fast-import.txt

@@ -45,10 +45,7 @@ OPTIONS
 
 --max-pack-size=<n>::
 	Maximum size of each output packfile.
-	The default is 4 GiB as that is the maximum allowed
-	packfile size (due to file format limitations). Some
-	importers may wish to lower this, such as to ensure the
-	resulting packfiles fit on CDs.
+	The default is unlimited.
 
 --big-file-threshold=<n>::
 	Maximum size of a blob that fast-import will attempt to