CHANGELOG: update for v0.27.8

CHANGELOG.md

+v0.27.8
+-------
+
+This is a bugfix release with the following change:
+
+- Negative gitignore rules should match git's behavior.  For example,
+  given a gitignore rule of `*.test` and a second gitignore rule of
+  `!dir/*`, we would incorrect apply the negation rules.  With this
+  fix, we behave like git.
+
+- Always provide custom transport implementations with the URL in the
+  action function.  v0.27.7 included a change that would erroneously
+  provide NULL to subsequent calls to the action function.  This is
+  fixed.
+
+- Fix several bugs parsing malformed commits and malformed trees.
+
+- Allow configuration file directory locations to be specified as
+  `/dev/null`.
+
+- Ensure that when an error occurs reading from the loose ODB backend
+  that we do not segfault.
+
+- Ensure that when a filter stream application fails that we do not
+  segfault.
+
+- Ensure that any configuration reading failures are propagated while
+  loading submodule information.
+
+- Peel annotated tags fully when creating an annotated commit.
+
+- Ensure that numbers are parsed correctly in a variety of places.
+
 v0.27.7
 -------