Add documentation for git-map-branches, git-map, git-nav-downstream,

docs/src/git-nav-upstream.txt

Index: docs/src/git-nav-upstream.txt
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+git-nav-upstream(1)
+=====================
+
+NAME
+----
+git-nav-upstream -
+include::_git-nav-upstream_desc.helper.txt[]
+
+SYNOPSIS
+--------
+[verse]
+'git nav-upstream'
+
+DESCRIPTION
+-----------
+
+'git-nav-upstream' takes the current branch, finds it\'s upstream branch, and
+checks that out.
+
+EXAMPLE
+-------
+
+[subs="quotes,attributes"]
+----
+[white]**$ git map-branches**
+[red]##origin/master##
+  [green]#cool_feature#
+    [aqua]**subfeature *{zwsp}**
+  [green]#frozen_changes#
+  [green]#master#
+[fuchsia]#{NO UPSTREAM}#
+  [green]#bogus_noparent#
+[white]**$ git nav-upstream**
+[white]**$ git map-branches**
+[red]##origin/master##
+  [aqua]**cool_feature *{zwsp}**
+    [green]#subfeature#
+  [green]#frozen_changes#
+  [green]#master#
+[fuchsia]#{NO UPSTREAM}#
+  [green]#bogus_noparent#
+----
+
+SEE ALSO
+--------
+linkgit:git-map-branches[1], linkgit:git-nav-downstream[1]
+
+include::_footer.txt[]
+
+// vim: ft=asciidoc noexpandtab: