[TYPO3-v4] Add version number to extension name in ext-folder and create a link to currently used version

[Christian Kuhn]

Hey,

another goody I'd like to hear your opinion about.

If downloading an extension from TER, it would be great to store the 
extension with the version number pending, and set a link 
"extensionname" to the new version.

Example:
typo3conf/ext/phpmyadmin-4.8.1 as d/l from TER
typo3conf/ext/phpmyadmin link to typo3conf/ext/phpmyadmin-4.8.1

Why?:
For us, typo3conf/ext is a SVN checkout (at least for project bigger 
than "trivial"). If we update extensions through em, svn is confused 
because of the missing .svn subdirectory, because em deletes the folder 
and writes the new version.

So, our current workflow if updating from TER is:
- Unload extension and hope BE does not fatal after that
- svn rm old extension
- Import new version from TER
- svn add new vanilla version

This process gets more complicated if we must handle local extension 
"hacks", then we need to diff out the hacks from svn, store them 
somewhere, import new version and re-apply the hacks.

*if* every new TER extension version gets a new directory within 
typo3conf/ext, the old one is not deleted, and we just link to the new 
version, all this would be much more simple: We can easily "svn merge" 
hacks from older versions, the import is easy, import doesn't destroy 
the .svn directories, and it's all transparent for svn. Even the 
link-change is under svn control.

Question is: Do you think something like that would be useful to be 
handled by core?
If yes, we'll think about a core solution (no promisses).
If not, we *will* hack up XCLASSES or an own em-fork to do that (plus 
additional implementation for automatic svn check-in and cleanup, and 
maybe handling of svn-external extensions).


Regards
Christian