Update draft release notes to 1.8.4

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/RelNotes/1.8.4.txt

@@ -35,6 +35,14 @@ Foreign interfaces, subsystems and ports.
 
 UI, Workflows & Features
 
+ * Various subcommands of "git submodule" refused to run from anywhere
+   other than the top of the working tree of the superproject, but
+   they have been taught to let you run from a subdirectory.
+
+ * "git diff" learned a mode that ignores hunks whose change consists
+   only of additions and removals of blank lines, which is the same as
+   "diff -B" (ignore blank lines) of GNU diff.
+
  * "git rm" gives a single message followed by list of paths to report
    multiple paths that cannot be removed.
 
@@ -108,6 +116,16 @@ UI, Workflows & Features
 
 Performance, Internal Implementation, etc.
 
+ * "git pack-refs" that races with new ref creation or deletion have
+   been susceptible to lossage of refs under right conditions, which
+   has been tightened up.
+
+ * We read loose and packed rerferences in two steps, but after
+   deciding to read a loose ref but before actually opening it to read
+   it, another process racing with us can unlink it, which would cause
+   us to barf.  The codepath has been updated to retry when such a
+   race is detected, instead of outright failing.
+
  * Uses of the platform fnmatch(3) function (many places in the code,
    matching pathspec, .gitignore and .gitattributes to name a few)
    have been replaced with wildmatch, allowing "foo/**/bar" that would
@@ -157,6 +175,11 @@ Unless otherwise noted, all the fixes since v1.8.3 in the maintenance
 track are contained in this release (see release notes to them for
 details).
 
+ * "git name-rev --refs=tags/v*" were forbidden, which was a bit
+   inconvenient (you had to give a pattern to match refs fully, like
+   --refs=refs/tags/v*).
+   (merge 98c5c4a nk/name-rev-abbreviated-refs later to maint).
+
  * "git apply" parsed patches that add new files, generated by
    programs other than Git, incorrectly.  This is an old breakage in
    v1.7.11 and will need to be merged down to the maintanance tracks.