docs: fix some antique example output

These diff-index and diff-tree sample outputs date back to
the first month of git's existence. The output format has
changed slightly since then, so let's have it match the
current output.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-diff-index.txt

@@ -96,8 +96,8 @@ show that. So let's say that you have edited `kernel/sched.c`, but
 have not actually done a 'git update-index' on it yet - there is no
 "object" associated with the new state, and you get:
 
-  torvalds@ppc970:~/v2.6/linux> git diff-index HEAD
-  *100644->100664 blob    7476bb......->000000......      kernel/sched.c
+  torvalds@ppc970:~/v2.6/linux> git diff-index --abbrev HEAD
+  :100644 100664 7476bb... 000000...      kernel/sched.c
 
 i.e., it shows that the tree has changed, and that `kernel/sched.c` has is
 not up-to-date and may contain new stuff. The all-zero sha1 means that to

Documentation/git-diff-tree.txt

@@ -138,8 +138,8 @@ so it can be used to name subdirectories.
 
 An example of normal usage is:
 
-  torvalds@ppc970:~/git> git diff-tree 5319e4......
-  *100664->100664 blob    ac348b.......->a01513.......      git-fsck-objects.c
+  torvalds@ppc970:~/git> git diff-tree --abbrev 5319e4
+  :100664 100664 ac348b... a01513...	git-fsck-objects.c
 
 which tells you that the last commit changed just one file (it's from
 this one: