Revision 780728

Backport reformattings and r780723:
Make KOpenWithDialog write to mimeapps.list when asked to remember an association between a mimetype and an existing application.

It still has to write a new .desktop file when the user types the name of a program without a .desktop file, or when checking "Run in terminal" (but in that case it's not a copy of another desktop file, so the previous fix to KConfig::copyTo is now unrelated to this code).
CCBUG: 154595