docs: Use :doc: role when linking to commands

This makes it so we link to the very top of the document instead of a
special anchor we manually include.

So clicking e.g. :doc:`string <cmds/string>` will link you to
cmds/string.html instead of cmds/string.html#cmd-string.

I would love to have a way to say "this document from the root of the
document path", but that doesn't appear to work, I tried
`/cmds/string`.

So we'll just have to use cmds/string in normal documents and plain
`string` from other commands.

doc_src/cmds/and.rst

@@ -15,7 +15,7 @@ Description
 
 ``and`` is used to execute a command if the previous command was successful (returned a status of 0).
 
-``and`` statements may be used as part of the condition in an :ref:`while <cmd-while>` or :ref:`if <cmd-if>` block.
+``and`` statements may be used as part of the condition in an :doc:`while <while>` or :doc:`if <if>` block.
 
 ``and`` does not change the current exit status itself, but the command it runs most likely will. The exit status of the last foreground command to exit can always be accessed using the :ref:`$status <variables-status>` variable.
 
@@ -33,5 +33,5 @@ The following code runs the ``make`` command to build a program. If the build su
 See Also
 --------
 
-- :ref:`or <cmd-or>` command
-- :ref:`not <cmd-not>` command
+- :doc:`or <or>` command
+- :doc:`not <not>` command