Documentation: move RelNotes into a directory of their own

There are 108 of them already.  That's a bit more than one third of
all the files in the Documentation directory already, and still growing.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/RelNotes/1.7.2.3.txt

@@ -0,0 +1,39 @@
+Git v1.7.2.3 Release Notes
+==========================
+
+Fixes since v1.7.2.2
+--------------------
+
+ * When people try insane things such as delta-compressing 4GiB files, we
+   threw an assertion failure.
+
+ * "git archive" gave the full commit ID for "$Format:%h$".
+
+ * "git fetch --tags" did not fetch tags when remote.<nick>.tagopt was set
+   to --no-tags.  The command line option now overrides the configuration
+   setting.
+
+ * "git for-each-ref --format='%(objectname:short)'" has been completely
+   broken for a long time.
+
+ * "git gc" incorrectly pruned a rerere record that was created long
+   time ago but still is actively and repeatedly used.
+
+ * "git log --follow -M -p" was seriously broken in 1.7.2, reporting
+   assertion failure.
+
+ * Running "git log" with an incorrect option started pager nevertheless,
+   forcing the user to dismiss it.
+
+ * "git rebase" did not work well when the user has diff.renames
+   configuration variable set.
+
+ * An earlier (and rather old) fix to "git rebase" against a rebased
+   upstream broke a more normal, non rebased upstream case rather badly,
+   attempting to re-apply patches that are already accepted upstream.
+
+ * "git submodule sync" forgot to update the superproject's config file
+   when submodule URL changed.
+
+ * "git pack-refs --all --prune" did not remove a directory that has
+   become empty.