kpatch-build: make xtrace output less verbose

With '--debug', most of the xtrace output shows the reading of the
.config and Module.symvers files, which isn't very useful and floods the
rest of the xtrace output.  Temporarily disable xtrace before reading
the files.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>

kpatch-build/kpatch-build

@@ -97,6 +97,18 @@ logger() {
 	fi
 }
 
+trace_on() {
+	if [[ $DEBUG -eq 1 ]] || [[ $DEBUG -ge 3 ]]; then
+		set -o xtrace
+	fi
+}
+
+trace_off() {
+	if [[ $DEBUG -eq 1 ]] || [[ $DEBUG -ge 3 ]]; then
+		set +o xtrace
+	fi
+}
+
 save_env() {
 	export -p | grep -wv -e 'OLDPWD=' -e 'PWD=' > "$ENVFILE"
 }
@@ -619,9 +631,7 @@ if [[ ${#PATCH_LIST[@]} -eq 0 ]]; then
 	exit 1
 fi
 
-if [[ $DEBUG -eq 1 ]] || [[ $DEBUG -ge 3 ]]; then
-	set -o xtrace
-fi
+trace_on
 
 if [[ -n "$SRCRPM" ]]; then
 	if  [[ -n "$ARCHVERSION" ]]; then
@@ -822,9 +832,11 @@ fi
 
 # kernel option checking
 
+trace_off "reading .config"
 # Don't check external file.
 # shellcheck disable=SC1090
 source "$CONFIGFILE"
+trace_on
 
 [[ -z "$CONFIG_DEBUG_INFO" ]] && die "kernel doesn't have 'CONFIG_DEBUG_INFO' enabled"
 
@@ -971,6 +983,7 @@ fi
 grep -q vmlinux "$KERNEL_SRCDIR/Module.symvers" || die "truncated $KERNEL_SRCDIR/Module.symvers file"
 
 if [[ -n "$CONFIG_MODVERSIONS" ]]; then
+	trace_off "reading Module.symvers"
 	while read -ra sym_line; do
 		if [[ ${#sym_line[@]} -lt 4 ]]; then
 			die "Malformed ${TEMPDIR}/Module.symvers file"
@@ -991,6 +1004,7 @@ if [[ -n "$CONFIG_MODVERSIONS" ]]; then
 			warn "Version disagreement for symbol ${sym}"
 		fi
 	done < "${TEMPDIR}/Module.symvers"
+	trace_on
 fi
 
 # Read as words, no quotes.