rpm: simplify applying of patches

The distros we support for RPM builds all have %autosetup support so we
can ditch the convoluted code for running git manually and use the RPM
defaults.
Reviewed-by: NMartin Kletzander <mkletzan@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>

libvirt.spec.in

@@ -993,43 +993,7 @@ Libvirt plugin for NSS for translating domain names into IP addresses.
 
 %prep
 
-%setup -q
-
-# Patches have to be stored in a temporary file because RPM has
-# a limit on the length of the result of any macro expansion;
-# if the string is longer, it's silently cropped
-%{lua:
-    tmp = os.tmpname();
-    f = io.open(tmp, "w+");
-    count = 0;
-    for i, p in ipairs(patches) do
-        f:write(p.."\n");
-        count = count + 1;
-    end;
-    f:close();
-    print("PATCHCOUNT="..count.."\n")
-    print("PATCHLIST="..tmp.."\n")
-}
-
-git init -q
-git config user.name rpm-build
-git config user.email rpm-build
-git config gc.auto 0
-git add .
-git commit -q -a --author 'rpm-build <rpm-build>' \
-           -m '%{name}-%{version} base'
-
-COUNT=$(grep '\.patch$' $PATCHLIST | wc -l)
-if [ $COUNT -ne $PATCHCOUNT ]; then
-    echo "Found $COUNT patches in $PATCHLIST, expected $PATCHCOUNT"
-    exit 1
-fi
-if [ $COUNT -gt 0 ]; then
-    xargs git am <$PATCHLIST || exit 1
-fi
-echo "Applied $COUNT patches"
-rm -f $PATCHLIST
-rm -rf .git
+%autosetup -S git_am
 
 %build
 %if ! %{supported_platform}