This topic describes the steps I use to upgrade TWiki 4 Dakar to TWiki 4 Edinburgh. They are based on assumption that the initial installation was done similarly to How I Setup TWiki412 On Dreamhost.
The first step is to install the latest TWiki release in a different directory
Check the configuration options in bin/configure to ensure they are similar or the same
Copy the data/.htpasswd file from the old install to the new, this will allow you to go ahead and log in
Check the TWiki.TWikiPreferences topic from the old install, it should be unmodified!
If it is modified you will want to copy only the modifications to Main.TWikiPreferences on the new install
Copy the TWiki configuration settings you wish to keep from the old Main.TWikiPreferences to the new Main.TWikiPreferences
You may wish to look up the default values for those settings in the new TWiki.TWikiPreferences to see if there are any notes about changes
Install and configure the plugins in the new install that you wish to keep from the old
You may want to check each plugin topic on the old install for custom settings and migrate those to the new install