Switch to VCS versioning

PKGBUILD

@@ -1,7 +1,7 @@
 # Maintainer: Drew DeVault <sir@cmpwn.com>
 pkgname=sway-git
 _pkgname=sway
-pkgver=1.0.0
+pkgver=r170.0d04189
 pkgrel=1
 license=('MIT')
 pkgdesc='i3 compatible window manager for Wayland'
@@ -13,6 +13,11 @@ url='https://github.com/SirCmpwn/sway'
 source=("${pkgname%-*}::git+https://github.com/SirCmpwn/sway.git")
 sha1sums=('SKIP')
 
+pkgver() {
+	cd "${srcdir}/${_pkgname}"
+	printf "r%s.%s" "$(git rev-list --count HEAD)" "$(git rev-parse --short HEAD)"
+}
+
 build() {
 	cd "${srcdir}/${_pkgname}"