config.txt: move pretty.* 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

@@ -381,15 +381,7 @@ include::config/pack.txt[]
 
 include::config/pager.txt[]
 
-pretty.<name>::
-	Alias for a --pretty= format string, as specified in
-	linkgit:git-log[1]. Any aliases defined here can be used just
-	as the built-in pretty formats could. For example,
-	running `git config pretty.changelog "format:* %H %s"`
-	would cause the invocation `git log --pretty=changelog`
-	to be equivalent to running `git log "--pretty=format:* %H %s"`.
-	Note that an alias with the same name as a built-in format
-	will be silently ignored.
+include::config/pretty.txt[]
 
 protocol.allow::
 	If set, provide a user defined default policy for all protocols which

Documentation/config/pretty.txt

@@ -0,0 +1,9 @@
+pretty.<name>::
+	Alias for a --pretty= format string, as specified in
+	linkgit:git-log[1]. Any aliases defined here can be used just
+	as the built-in pretty formats could. For example,
+	running `git config pretty.changelog "format:* %H %s"`
+	would cause the invocation `git log --pretty=changelog`
+	to be equivalent to running `git log "--pretty=format:* %H %s"`.
+	Note that an alias with the same name as a built-in format
+	will be silently ignored.