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/concepts.rst b/doc/source/user/concepts.rst
index 6197396..318de09 100644
--- a/doc/source/user/concepts.rst
+++ b/doc/source/user/concepts.rst
@@ -40,7 +40,8 @@
configured with any number of reporters. See :ref:`drivers` for a
full list of available reporters.
-The items enqueued into a pipeline are each associated with a git ref.
+The items enqueued into a pipeline are each associated with a
+`git ref <https://git-scm.com/book/en/v2/Git-Internals-Git-References>`_.
That ref may point to a proposed change, or it may be the tip of a
branch or a tag. The triggering event determines the ref, and whether
it represents a proposed or merged commit. Zuul prepares the ref for
@@ -67,7 +68,7 @@
change appears.
Jobs specify the type and quantity of nodes which they require.
-Before executing each job, Zuul will contact it's companion program,
+Before executing each job, Zuul will contact its companion program,
Nodepool, to supply them. Nodepool may be configured to supply static
nodes or contact cloud providers to create or delete nodes as
necessary. The types of nodes available to Zuul are determined by the
@@ -80,6 +81,6 @@
script) or sophisticated deployment scenarios. When Zuul runs
Ansible, it attempts to do so in a manner most similar to the way that
Ansible might be used to orchestrate remote systems. Ansible itself
-is run on the executor and acts remotely upon the test nodes supplied
-to a job. This facilitates continuous delivery by making it possible
-to use the same Ansible playbooks in testing and production.
+is run on the :ref:`executor <executor>` and acts remotely upon the test
+nodes supplied to a job. This facilitates continuous delivery by making it
+possible to use the same Ansible playbooks in testing and production.