Use same pre-release system as in other GNOME packages

It just makes it easier to do scripting to update packages if they all
follow the same pattern.

gnome-tweaks.spec

@@ -1,17 +1,15 @@
-%global prerelease beta
+%global tarball_version %%(echo %{version} | tr '~' '.')
-
+%global major_version %%(cut -d '.' -f 1 <<<%{tarball_version})
-%global _version %(cut -d "~" -f 1 <<<%{version})
-%global majorversion %(cut -d "." -f 1-2 <<<%{_version})
 
 Name:           gnome-tweaks
-Version:        40%{?prerelease:~%{prerelease}}
+Version:        40~beta
-Release:        2%{?dist}
+Release:        3%{?dist}
 Summary:        Customize advanced GNOME 3 options
 
 # Software is GPLv3, Appdata file is CC0-1.0
 License:        GPLv3 and CC0
 URL:            https://wiki.gnome.org/Apps/Tweaks
-Source0:        https://download.gnome.org/sources/%{name}/%{majorversion}/%{name}-%{_version}%{?prerelease:.%{prerelease}}.tar.xz
+Source0:        https://download.gnome.org/sources/%{name}/%{major_version}/%{name}-%{tarball_version}.tar.xz
 
 BuildRequires:  desktop-file-utils
 BuildRequires:  gettext
@@ -42,7 +40,7 @@ and extension, etc.
 
 
 %prep
-%autosetup -n %{name}-%{_version}%{?prerelease:.%{prerelease}}
+%autosetup -n %{name}-%{tarball_version}
 
 
 %build
@@ -86,6 +84,9 @@ appstream-util validate-relax --nonet $RPM_BUILD_ROOT/%{_datadir}/metainfo/*.app
 
 
 %changelog
+* Thu Feb 18 2021 Kalev Lember <klember@redhat.com> - 40~beta-3
+- Use same pre-release system as in other GNOME packages
+
 * Wed Feb 17 2021 Kalev Lember <klember@redhat.com> - 40~beta-2
 - Require libhandy1 instead of libhandy