Emilda 1.2.x releases are stable bug fix releases. As such, they only fixes a few minor code issues. Upgrading to 1.2.x can be done by simply overwriting the contents of the existing src folder with the contents of the new src folder (make sure you don't have anything else than source files in that folder).
The easiest way, however, is to use the supplied 1.2.x patch. Download the patch, save it in your current emilda src folder (the one with all the .php files) and issue the following command (in the src folder):
gunzip emilda-1.2.x.patch.gz patch -p2 < emilda-1.2.x.patch
If there is an emilda-1.2.x-lang.patch.gz file available, the language files have changed too. Download this patch, save it in your emilda lang folder and issue the following command (in the lang folder):
gunzip emilda-1.2.x-lang.patch.gz patch -p2 < emilda-1.2.x-lang.patch
After this the new language files need to be compiled as usual.
Watch out for any errors or warnings. After this run setup.php to make sure your system is up-to-date. If everything was successful, you should have a working Emilda 1.2.x environment.
This is only required for Emilda 1.2.1.
The zebra folder has changed in 1.2.1. Turn off your zebra server. Make sure you don't loose your records folder and replace your existing zebra folder with the new one (the tab/bib1.att file has changed). After the upgrade issue the following commands in the zebra root folder:
zebraidx init zebraidx -g emilda update records zebraidx commit
If everything went smoothly, restart zebra.