config.txt: move fastimport.* to a separate file

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -323,14 +323,7 @@ include::config/diff.txt[]
 
 include::config/difftool.txt[]
 
-fastimport.unpackLimit::
-	If the number of objects imported by linkgit:git-fast-import[1]
-	is below this limit, then the objects will be unpacked into
-	loose object files.  However if the number of imported objects
-	equals or exceeds this limit then the pack will be stored as a
-	pack.  Storing the pack from a fast-import can make the import
-	operation complete faster, especially on slow filesystems.  If
-	not set, the value of `transfer.unpackLimit` is used instead.
+include::config/fastimport.txt[]
 
 include::fetch-config.txt[]
 

Documentation/config/fastimport.txt

@@ -0,0 +1,8 @@
+fastimport.unpackLimit::
+	If the number of objects imported by linkgit:git-fast-import[1]
+	is below this limit, then the objects will be unpacked into
+	loose object files.  However if the number of imported objects
+	equals or exceeds this limit then the pack will be stored as a
+	pack.  Storing the pack from a fast-import can make the import
+	operation complete faster, especially on slow filesystems.  If
+	not set, the value of `transfer.unpackLimit` is used instead.