This action is shown when plugin is loaded, but that's when it has folder .svn

There is a new public virtual function for out-of-version-control folders, https://phabricator.kde.org/D29041

Check that repoPath looks like a remote svn repo url with schemes svn:/ https:/ or http:/ (can svn use others ?)

Don't need to else here.
A user might have the url in the clipboard and the target dir selected.

Can reuse variable stripped

If we could add some progress dialog of some kind, allowing the user to kill the process.

Yes, that is correct, this is the most common use strategy.
The idea was "if clipboard contains correct URL set it through on_leRepository_textChanged() which sets work directory path, if no URL just set the work directory path to the current dir".
Do you think about something better?

This is a huge problem now and it is in todo list.
SvnCommands should become a singleton with signal-slots connection to run svn process and not block Dolphin main thread.
I think this is a separate commit change.
If we can't accept this without a normal multithreading it's ok i will try to implement it first.

http://svnbook.red-bean.com/en/1.2/svn-book.html#svn.basic.in-action.wc.tbl-1
Ok, we can check probably with regex. Some basic checks: this is URL (QUrl().isValid()) and starts correct.

Do you really need QObject:: here ?

And here ?

This is for slots autoconnection: https://doc.qt.io/qt-5/qmetaobject.html#connectSlotsByName
I can manually connect if needed.