[mythtv] Building rpms for master

[John Pilkington]

The specfile at

https://github.com/MythTV/packaging/blob/master/rpm/mythtv.spec

includes
Source0: http://www.mythtv.org/mc/mythtv-%{version}.tar.bz2
Source1: http://www.mythtv.org/mc/mythplugins-%{version}.tar.bz2

I have mythtv-master.tar.gz, downloaded yesterday from

https://codeload.github.com/MythTV/mythtv/tar.gz/master

which looks as if it ought to provide all that content; its 
EXPORTED_VERSION reads

SOURCE_VERSION="18cd383"
BRANCH=" (HEAD, master)"

but rpmbuild -bp, run from the SPECS directory, seems to need both 
Source0 and Source1.  It runs if I define them both as 
mythtv-master.tar.gz but unpacks twice and then fails.

+ /usr/bin/gzip -dc /home/john/rpmbuild/SOURCES/mythtv-master.tar.gz
+ /bin/tar -xf -
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ /bin/tar -xf -
+ /usr/bin/gzip -dc /home/john/rpmbuild/SOURCES/mythtv-master.tar.gz
+ STATUS=0
+ '[' 0 -ne 0 ']'
+ /bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ '[' lib '!=' lib ']'
+ cd mythtv
/var/tmp/rpm-tmp.cnSSeM: line 55: cd: mythtv: No such file or directory
error: Bad exit status from /var/tmp/rpm-tmp.cnSSeM (%prep)

RPM build errors:
     Bad exit status from /var/tmp/rpm-tmp.cnSSeM (%prep)

What ought I to be doing?

TIA

John P