Docu update

doc/yupdate.md

@@ -23,12 +23,30 @@ but they are usually not trivial and need special preparations.
 For this reason we created a special `yupdate` script which makes
 the process easier.
 
-**Note**: After patching the installer the `yupdate` script disables
+However, in some cases this easier way cannot be used, see the
+[limitations](#limitations) section below.
+
+
+## Self-update
+
+After patching the installer the `yupdate` script disables
 the YaST self-update feature because it could conflict with it
-and overwrite the changes. If you need some changes from the self-update
-then use the `startshell=1` boot option, start the installer and
-allow the self-update step to finish, then abort the installation
-and use the `ypdate` script to apply the changes on top of the self-update.
+and overwrite the changes.
+
+If you need some changes from the self-update then use the `startshell=1`
+boot option, start the installer and allow the self-update step to finish,
+then abort the installation and use the `ypdate` script to apply the
+changes on top of the self-update.
+
+##  Warning
+
+:warning: **Patching the installer with the `yupdate` script makes
+the installation unsupported!** :warning:
+
+The script is intended for developers to test new features or bug fixes.
+
+It can be used by customers for testing as well, but it should not be used
+on production systems!
 
 ## Installation
 
@@ -63,23 +81,24 @@ yupdate overlay create <dir>
 ```
 
 This will create a writable overlay above the specified directory. If you do not
-specify any directory it will create writable overlays for the default YaST directories.
+specify any directory it will create writable overlays for the default YaST
+directories.
 
 Then you can easily edit the files using the included `vim` editor
 or by other tools like `sed` or overwrite by external files.
 
 ### Patch YaST from GitHub Sources
 
-To update or install an YaST package directly from the GitHub source code repository
-use command
+To update or install an YaST package directly from the GitHub source code
+repository use command
 
 ```shell
 yupdate patch <github_slug> <branch>
 ```
 
-where `github_slug` is a `user`/`repository` name, if the `user` value is missing
-the default "yast" is used. The `branch` in the source branch to install, for example
-`master` or `SLE-15-SP2`.
+where `github_slug` is a `user`/`repository` name, if the `user` value is
+missing the default "yast" is used. The `branch` in the source branch to
+install, for example `master` or `SLE-15-SP2`.
 
 
 #### Examples
@@ -111,8 +130,8 @@ In that case run
 rake server
 ```
 
-in your YaST module Git checkout. This will run a web server providing source tarball
-similar to the GitHub archive used in the previous case.
+in your YaST module Git checkout. This will run a web server providing source
+tarball similar to the GitHub archive used in the previous case.
 
 *Note: You need "yast-rake" Ruby gem version 0.2.37 or newer.*
 
@@ -191,7 +210,6 @@ yupdate overlay reset
 This will remove *all* OverlayFS mounts and restore the system to the original
 state.
 
-
 ## Limitations
 
 - The script only works with Ruby source files, it cannot compile and
@@ -201,7 +219,6 @@ state.
   it does not work with autotools based packages (again, autoconf/automake
   are also missing in the inst-sys)
 
-
 ## Alternative
 
 1. For all repos, run `rake osc:build`
@@ -233,3 +250,9 @@ editor backup files, etc...
 
 This saves some memory as we do not need to shadow the not modified files
 with the same content.
+
+### Logging
+
+The messages printed on the console are also saved in the `y2log` file.
+That means it should be easy to find out that someone patched the installer
+when analyzing logs from a bug report.