Doc improvements on user guide
This change:
* fixes some spelling issues
* externally links to a document describing what a 'git ref' is
* links to executor document at the first reference to it
* links to independent pipeline at the first reference to it
Change-Id: I3f2247deac15fd15c9dead6cba537d7b17e8491f
diff --git a/doc/source/user/gating.rst b/doc/source/user/gating.rst
index c1d04a7..795df72 100644
--- a/doc/source/user/gating.rst
+++ b/doc/source/user/gating.rst
@@ -227,7 +227,8 @@
A given dependent pipeline may have as many shared change queues as
necessary, so groups of related projects may share a change queue
-without interfering with unrelated projects. Independent pipelines do
+without interfering with unrelated projects.
+:value:`Independent pipelines <pipeline.manager.independent>` do
not use shared change queues, however, they may still be used to test
changes across projects using cross-project dependencies.