Add links some updates.

Author: rouilj

doc/admin_guide.txt

@@ -556,8 +556,10 @@ it to be elsewhere) will then complete the backup.
 Software Upgrade
 ----------------
 
-Always make a backup of your tracker before upgrading software. Steps you may
-take:
+.. _make a backup: #tracker-backup
+
+Always `make a backup`_ of your tracker before upgrading software.
+Steps you may take:
 
 1. Install pytest and ensure that the unit tests run on your system
    (using your preferred python version)::
@@ -576,11 +578,11 @@ take:
 
     python setup.py install
 
-6. Follow the steps in the `upgrading documentation`_ for the new version of
-   the software in the copied.
+6. Follow the steps in the `upgrading documentation`_ for all the
+   version between your original version and th new version.
 
-   Usually you will be asked to run `roundup_admin migrate` on your tracker
-   before you allow users to start accessing the tracker.
+   Usually you should run `roundup_admin -i <tracker_home> migrate`
+   on your tracker(s) before you allow users to start accessing the tracker.
 
    It's safe to run this even if it's not required, so just get into the
    habit.
@@ -591,7 +593,6 @@ reinstall the older version of the sofware using the same install command::
 
     python setup.py install
 
-
 .. index:: database; convert from one database backend to another
    single: roundup-admin; import and export
 

doc/upgrading.txt

@@ -12,7 +12,7 @@ Upgrading to newer versions of Roundup
 
 Please read each section carefully and edit your tracker home files
 accordingly. Note that there is information about upgrade procedures in the
-`administration guide`_.
+`administration guide`_ in the `Software Upgrade`_ section.
 
 If a specific version transition isn't mentioned here (eg. 0.6.7 to 0.6.8)
 then you don't need to do anything. If you're upgrading from 0.5.6 to
@@ -3466,3 +3466,4 @@ copy.
 .. _PostgreSQL's full text search: https://www.postgresql.org/docs/current/textsearch.html
 .. _`administration guide notes on native-fts`: admin_guide.html#configuring-native-fts-full-text-search
 .. _Configuring Compression: admin_guide.html#configuring-compression
+.. _Software Upgrade: admin_guide.html#software-upgrade