Documentation/config/fastimport.txt

   1 fastimport.unpackLimit::
   2         If the number of objects imported by linkgit:git-fast-import[1]
   3         is below this limit, then the objects will be unpacked into
   4         loose object files.  However if the number of imported objects
   5         equals or exceeds this limit then the pack will be stored as a
   6         pack.  Storing the pack from a fast-import can make the import
   7         operation complete faster, especially on slow filesystems.  If
   8         not set, the value of `transfer.unpackLimit` is used instead.