Documentation about exclude/ignore files

Use .git/info/exclude in the example in git-ls-files.txt,
instead of .git/ignore, and update the list of commands looking
at .git/info/exclude in repository-layout.txt.

Signed-off-by: Matthias Lederhofer <matled@gmx.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-ls-files.txt

@@ -207,7 +207,7 @@ An exclude pattern is of the following format:
 An example:
 
 --------------------------------------------------------------
-    $ cat .git/ignore
+    $ cat .git/info/exclude
     # ignore objects and archives, anywhere in the tree.
     *.[oa]
     $ cat Documentation/.gitignore
@@ -217,7 +217,7 @@ An example:
     !foo.html
     $ git-ls-files --ignored \
         --exclude='Documentation/*.[0-9]' \
-        --exclude-from=.git/ignore \
+        --exclude-from=.git/info/exclude \
         --exclude-per-directory=.gitignore
 --------------------------------------------------------------
 

Documentation/repository-layout.txt

@@ -120,9 +120,11 @@ info/grafts::
 
 info/exclude::
 	This file, by convention among Porcelains, stores the
-	exclude pattern list.  `git status` looks at it, but
-	otherwise it is not looked at by any of the core git
-	commands.
+	exclude pattern list. `.gitignore` is the per-directory
+	ignore file.  `git status`, `git add`, `git rm` and `git
+	clean` look at it but the core git commands do not look
+	at it.  See also: gitlink:git-ls-files[1] `--exclude-from`
+	and `--exclude-per-directory`.
 
 remotes::
 	Stores shorthands to be used to give URL and default