MarsSeed [1] filed a deletion request for qtcreator-src-git [2]: Unneeded orphan VCS package. AUR has a proper qtcreator-git, and repo carries qtcreator and qtcreator-devel, the latter contains the development source files needed for building plugins.
[1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/qtcreator-src-git/
