patch DHCP NM dispatcher for distribution

Patch the upstream example `nm-dispatcher.dhcp` with
Fedora/RHEL-specific behavior including exiting if a dhclient
install is detected, and using the /etc/sysconfig paths.

Originally part of work for fixing integration between the
NetworkManager internal DHCP client and chrony:
https://bugzilla.redhat.com/show_bug.cgi?id=1800901

chrony-nm-dispatcher-dhcp.patch

@@ -0,0 +1,52 @@
+From e0c6457fd42252f88ec60d16582b7b6e6fb04f41 Mon Sep 17 00:00:00 2001
+From: Robert Fairley <rfairley@redhat.com>
+Date: Wed, 17 Jun 2020 10:14:19 -0400
+Subject: [PATCH] examples/nm-dispatcher.dhcp: use sysconfig, detect dhclient
+
+Use the PEERNTP and NTPSERVERARGS environment variables from
+/etc/sysconfig/network{-scripts}. Detect a dhclient install to avoid a
+redundant operation with the 11-dhclient NM dispatcher in the
+dhcp-client package.
+---
+ examples/chrony.nm-dispatcher.dhcp | 15 ++++++++++++++-
+ 1 file changed, 14 insertions(+), 1 deletion(-)
+
+diff --git a/examples/chrony.nm-dispatcher.dhcp b/examples/chrony.nm-dispatcher.dhcp
+index 6ea4c37..878e72f 100644
+--- a/examples/chrony.nm-dispatcher.dhcp
++++ b/examples/chrony.nm-dispatcher.dhcp
+@@ -6,6 +6,11 @@
+ 
+ export LC_ALL=C
+ 
++# If a dhclient installation is present, avoid a redundant operation
++# with dhclient which handles NTP server config through its own
++# NetworkManager dispatcher script 11-dhclient.
++[ -e /usr/sbin/dhclient ] && exit 0
++
+ interface=$1
+ action=$2
+ 
+@@ -17,10 +22,18 @@ dhcp_server_file=$server_dir/$interface.sources
+ # DHCP4_NTP_SERVERS is passed from DHCP options by NetworkManager.
+ nm_dhcp_servers=$DHCP4_NTP_SERVERS
+ 
++[ -f /etc/sysconfig/network ] && . /etc/sysconfig/network
++[ -f /etc/sysconfig/network-scripts/ifcfg-"${interface}" ] && \
++    . /etc/sysconfig/network-scripts/ifcfg-"${interface}"
++
+ add_servers_from_dhcp() {
+     rm -f "$dhcp_server_file"
++
++    # Don't add NTP servers if PEERNTP=no specified; return early.
++    [ "$PEERNTP" = "no" ] && return
++
+     for server in $nm_dhcp_servers; do
+-        echo "server $server $default_server_options" >> "$dhcp_server_file"
++        echo "server $server ${NTPSERVERARGS:-$default_server_options}" >> "$dhcp_server_file"
+     done
+     $chronyc reload sources > /dev/null 2>&1 || :
+ }
+-- 
+2.26.2
+

chrony.spec

@@ -21,6 +21,10 @@ Source6:        chrony-dnssrv@.timer
 Source10:       https://github.com/mlichvar/clknetsim/archive/%{clknetsim_ver}/clknetsim-%{clknetsim_ver}.tar.gz
 %{?gitpatch:Patch0: chrony-%{version}%{?prerelease}-%{gitpatch}.patch.gz}
 
+# add Fedora/RHEL-specific bits to DHCP dispatcher, including
+# deferring to dhclient if installled, and using /etc/sysconfig
+Patch1:         chrony-nm-dispatcher-dhcp.patch
+
 BuildRequires:  libcap-devel libedit-devel nettle-devel pps-tools-devel
 %ifarch %{ix86} x86_64 %{arm} aarch64 mipsel mips64el ppc64 ppc64le s390 s390x
 BuildRequires:  libseccomp-devel
@@ -52,6 +56,7 @@ service to other computers in the network.
 %{gpgverify} --keyring=%{SOURCE2} --signature=%{SOURCE1} --data=%{SOURCE0}
 %setup -q -n %{name}-%{version}%{?prerelease} -a 10
 %{?gitpatch:%patch0 -p1}
+%patch1 -p1 -b .nm-dispatcher-dhcp
 
 %{?gitpatch: echo %{version}-%{gitpatch} > version.txt}
 
@@ -61,6 +66,7 @@ md5sum -c <<-EOF | (! grep -v 'OK$')
         dcad37a5f1aae2d2ea7b935f279e0eca  examples/chrony.conf.example2
         96999221eeef476bd49fe97b97503126  examples/chrony.keys.example
         6a3178c4670de7de393d9365e2793740  examples/chrony.logrotate
+        63aa1412fd9044bde26475e4a9770fbf  examples/chrony.nm-dispatcher.dhcp
         8f5a98fcb400a482d355b929d04b5518  examples/chrony.nm-dispatcher.onoffline
         32c34c995c59fd1c3ad1616d063ae4a0  examples/chronyd.service
 EOF
@@ -128,7 +134,9 @@ install -m 644 -p examples/chrony.logrotate \
 install -m 644 -p examples/chronyd.service \
         $RPM_BUILD_ROOT%{_unitdir}/chronyd.service
 install -m 755 -p examples/chrony.nm-dispatcher.onoffline \
-        $RPM_BUILD_ROOT%{_prefix}/lib/NetworkManager/dispatcher.d/20-chrony
+        $RPM_BUILD_ROOT%{_prefix}/lib/NetworkManager/dispatcher.d/20-chrony-onoffline
+install -m 755 -p examples/chrony.nm-dispatcher.dhcp \
+        $RPM_BUILD_ROOT%{_prefix}/lib/NetworkManager/dispatcher.d/20-chrony-dhcp
 install -m 644 -p examples/chrony-wait.service \
         $RPM_BUILD_ROOT%{_unitdir}/chrony-wait.service
 install -m 644 -p %{SOURCE5} $RPM_BUILD_ROOT%{_unitdir}/chrony-dnssrv@.service