Add RelNotes 1.5.1

Instead of running around listing the changes near the release,
let's keep things nicely organized by summarizing the changes as
we merge things to the 'master' branch.

I haven't decided how well this will go with people's patch
submission procedure yet --- we'll play it by the ear and see
what happens.

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/RelNotes-1.5.1.txt

@@ -0,0 +1,39 @@
+GIT v1.5.1 Release Notes
+========================
+
+Updates since v1.5.0
+--------------------
+
+* Deprecated commands and options.
+
+  - git-diff-stages and git-resolve have been removed.
+
+* New commands and options.
+
+  - "git log" and friends take --reverse.  This makes output
+    that typically goes reverse order in chronological order.
+    "git shortlog" usually lists commits in chronological order,
+    but with "--reverse", they are shown in reverse
+    chronological order.
+
+  - "git diff" learned --ignore-space-at-eol.  This is a weaker
+    form of --ignore-space-change.
+
+* Updated behaviour of existing commands.
+
+ - "git diff" outputs a trailing HT when pathnames have embedded
+   SP on +++/--- header lines, in order to help "GNU patch" to
+   parse its output.  "git apply" was already updated to accept
+   this modified output format since ce74618d (Sep 22, 2006).
+
+* Hooks
+
+ - The sample update hook to show how to send out notification
+   e-mail was updated to show only new commits that appeared in
+   the repository.  Earlier, it showed new commits that appeared
+   on the branch.
+
+--
+O=v1.5.0-20-ga44a0c9
+echo O=`git describe master`
+git shortlog --no-merges $O..