Automatically call %python_provide

This allows us to drop the %python_provide macro from most spec files,
except where we want to use it for virtual provides or empty packages.

pythonname.attr

@@ -0,0 +1,20 @@
+%__pythonname_provides() %{lua:
+    -- this macro is called for each file in a package, the path being in %1
+    -- but we don't need to know the path, so we would get for each file: Macro %1 defined but not used within scope
+    -- in here, we expand %name conditionally on %1 to suppress the warning
+    local name = rpm.expand('%{?1:%{name}}')
+    -- a structure that knows what names were already processed, so we can end early
+    if __pythonname_beenthere == nil then
+        __pythonname_beenthere = {}
+    end
+    -- we save ourselves a trip to %python_provide if we have already been there
+    if __pythonname_beenthere[name] == nil then
+        local python_provide = rpm.expand('%{?python_provide:%python_provide %{name}}')
+        for provides in python_provide:gmatch('Provides:[ \\t]+([^\\n]+)') do
+          print(provides .. " ")
+        end
+        __pythonname_beenthere[name] = true
+    end
+}
+
+%__pythonname_path ^/