documentation: clarify direction of core.autocrlf

The description for core.autocrlf refers to reads from / writes to
"the filesystem", the only use of this rather ambiguous term, which
technically could be referring to the git object database. (All other
mentions are part of phrases such as "..filesystems (like NFS)..").

Other sections, including the section on core.safecrlf, use the term
"work tree" for the same purpose as the term "the filesystem" is used in
the core.autocrlf section, so that seems like a good alternative, which
makes it clearer what direction the addition/removal of CR characters
occurs in.

Signed-off-by: Will Palmer <wmpalmer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -198,11 +198,11 @@ core.quotepath::
 
 core.autocrlf::
 	If true, makes git convert `CRLF` at the end of lines in text files to
-	`LF` when reading from the filesystem, and convert in reverse when
-	writing to the filesystem.  The variable can be set to
+	`LF` when reading from the work tree, and convert in reverse when
+	writing to the work tree.  The variable can be set to
 	'input', in which case the conversion happens only while
-	reading from the filesystem but files are written out with
-	`LF` at the end of lines.  A file is considered
+	reading from the work tree but files are written out to the work
+	tree with `LF` at the end of lines.  A file is considered
 	"text" (i.e. be subjected to the autocrlf mechanism) based on
 	the file's `crlf` attribute, or if `crlf` is unspecified,
 	based on the file's contents.  See linkgit:gitattributes[5].