doc: document go get -f flag in 1.4 release notes
LGTM=r, rsc
R=r, rsc, adg
CC=golang-codereviews
https://golang.org/cl/168890043
diff --git a/doc/go1.4.html b/doc/go1.4.html
index cb2280c..3310117 100644
--- a/doc/go1.4.html
+++ b/doc/go1.4.html
@@ -372,6 +372,15 @@
</p>
<p>
+To complement this new feature, a check has been added at update time to verify
+that the local package's remote repository matches that of its custom import.
+The <code>go</code> <code>get</code> <code>-u</code> command will fail to
+update a package if its remote repository has changed since it was first
+downloaded.
+The new <code>-f</code> flag overrides this check.
+</p>
+
+<p>
Further information is in
<a href="http://golang.org/s/go14customimport">the design document</a>.
</p>
