Documentation: describe --thin more accurately

The description for --thin was misleading and downright wrong. Correct
it with some inspiration from the description of index-pack's --fix-thin
and some background information from Nicolas Pitre <nico@fluxnic.net>.

Signed-off-by: Stephen Boyd <bebarino@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-fetch-pack.txt

@@ -44,8 +44,8 @@ OPTIONS
 	locked against repacking.
 
 --thin::
-	Spend extra cycles to minimize the number of objects to be sent.
-	Use it on slower connection.
+	Fetch a "thin" pack, which records objects in deltified form based
+	on objects not included in the pack to reduce network traffic.
 
 --include-tag::
 	If the remote side supports it, annotated tags objects will

Documentation/git-index-pack.txt

@@ -46,14 +46,10 @@ OPTIONS
 	'git repack'.
 
 --fix-thin::
-	It is possible for 'git pack-objects' to build
-	"thin" pack, which records objects in deltified form based on
-	objects not included in the pack to reduce network traffic.
-	Those objects are expected to be present on the receiving end
-	and they must be included in the pack for that pack to be self
-	contained and indexable. Without this option any attempt to
-	index a thin pack will fail. This option only makes sense in
-	conjunction with --stdin.
+	Fix a "thin" pack produced by `git pack-objects --thin` (see
+	linkgit:git-pack-objects[1] for details) by adding the
+	excluded objects the deltified objects are based on to the
+	pack. This option only makes sense in conjunction with --stdin.
 
 --keep::
 	Before moving the index into its final destination

Documentation/git-pack-objects.txt

@@ -21,16 +21,21 @@ DESCRIPTION
 Reads list of objects from the standard input, and writes a packed
 archive with specified base-name, or to the standard output.
 
-A packed archive is an efficient way to transfer set of objects
-between two repositories, and also is an archival format which
-is efficient to access.  The packed archive format (.pack) is
-designed to be self contained so that it can be unpacked without
-any further information, but for fast, random access to the objects
-in the pack, a pack index file (.idx) will be generated.
+A packed archive is an efficient way to transfer a set of objects
+between two repositories as well as an access efficient archival
+format.  In a packed archive, an object is either stored as a
+compressed whole or as a difference from some other object.
+The latter is often called a delta.
 
-Placing both in the pack/ subdirectory of $GIT_OBJECT_DIRECTORY (or
+The packed archive format (.pack) is designed to be self-contained
+so that it can be unpacked without any further information. Therefore,
+each object that a delta depends upon must be present within the pack.
+
+A pack index file (.idx) is generated for fast, random access to the
+objects in the pack. Placing both the index file (.idx) and the packed
+archive (.pack) in the pack/ subdirectory of $GIT_OBJECT_DIRECTORY (or
 any of the directories on $GIT_ALTERNATE_OBJECT_DIRECTORIES)
-enables git to read from such an archive.
+enables git to read from the pack archive.
 
 The 'git unpack-objects' command can read the packed archive and
 expand the objects contained in the pack into "one-file
@@ -38,10 +43,6 @@ one-object" format; this is typically done by the smart-pull
 commands when a pack is created on-the-fly for efficient network
 transport by their peers.
 
-In a packed archive, an object is either stored as a compressed
-whole, or as a difference from some other object.  The latter is
-often called a delta.
-
 
 OPTIONS
 -------
@@ -179,6 +180,16 @@ base-name::
 	Add --no-reuse-object if you want to force a uniform compression
 	level on all data no matter the source.
 
+--thin::
+	Create a "thin" pack by omitting the common objects between a
+	sender and a receiver in order to reduce network transfer. This
+	option only makes sense in conjunction with --stdout.
++
+Note: A thin pack violates the packed archive format by omitting
+required objects and is thus unusable by git without making it
+self-contained. Use `git index-pack --fix-thin`
+(see linkgit:git-index-pack[1]) to restore the self-contained property.
+
 --delta-base-offset::
 	A packed archive can express base object of a delta as
 	either 20-byte object name or as an offset in the

Documentation/git-push.txt

@@ -141,9 +141,10 @@ useful if you write an alias or script around 'git push'.
 
 --thin::
 --no-thin::
-	These options are passed to 'git send-pack'.  Thin
-	transfer spends extra cycles to minimize the number of
-	objects to be sent and meant to be used on slower connection.
+	These options are passed to linkgit:git-send-pack[1]. A thin transfer
+	significantly reduces the amount of sent data when the sender and
+	receiver share many of the same objects in common. The default is
+	\--thin.
 
 -v::
 --verbose::

Documentation/git-send-pack.txt

@@ -48,8 +48,8 @@ OPTIONS
 	Run verbosely.
 
 --thin::
-	Spend extra cycles to minimize the number of objects to be sent.
-	Use it on slower connection.
+	Send a "thin" pack, which records objects in deltified form based
+	on objects not included in the pack to reduce network traffic.
 
 <host>::
 	A remote host to house the repository.  When this