criu --help: print a proper list of features

Remove that weird special case from check_add_feature() function, making
it a separate pr_check_features(), which prints a SEP-separated list of
feature names, obeying the max WIDTH, and prepending each line with
OFFSET. That way, we have a decept --help output:

  --feature FEAT        only check a particular feature, one of:
                            mnt_id, mem_dirty_track, aio_remap, timerfd, tun,
                            userns, fdinfo_lock, seccomp_suspend,
                            seccomp_filters, loginuid, cgroupns, autofs

Alternatively, we could just drop the functionality of showing all the
individual features to check.

[v2: use %s in pr_msg to fix a -Wformat-security warning]
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cr-check.c

@@ -1113,16 +1113,33 @@ static struct feature_list feature_list[] = {
 	{ NULL, NULL },
 };
 
-int check_add_feature(char *feat)
+void pr_check_features(const char *offset, const char *sep, int width)
 {
 	struct feature_list *fl;
+	int pos = width + 1;
+	int sep_len = strlen(sep);
+	int offset_len = strlen(offset);
+
+	for (fl = feature_list; fl->name; fl++) {
+		int len = strlen(fl->name);
 
-	if (!strcmp(feat, "list")) {
-		for (fl = feature_list; fl->name; fl++)
-			pr_msg("%s ", fl->name);
-		pr_msg("\n");
-		return 1;
+		if (pos + len + sep_len > width) {
+			pr_msg("\n%s", offset);
+			pos = offset_len;
+		}
+		pr_msg("%s", fl->name);
+		pos += len;
+		if ((fl + 1)->name) { // not the last item
+			pr_msg("%s", sep);
+			pos += sep_len;
+		}
 	}
+	pr_msg("\n");
+}
+
+int check_add_feature(char *feat)
+{
+	struct feature_list *fl;
 
 	for (fl = feature_list; fl->name; fl++) {
 		if (!strcmp(feat, fl->name)) {

criu/crtools.c

@@ -906,7 +906,7 @@ usage:
 "  --all                 same as --extra --experimental\n"
 "  --feature FEAT        only check a particular feature, one of:"
 	);
-	check_add_feature("list");
+	pr_check_features("                            ", ", ", 80);
 	pr_msg(
 "\n"
 "* Logging:\n"

criu/include/crtools.h

@@ -25,5 +25,6 @@ extern int cr_exec(int pid, char **opts);
 extern int cr_dedup(void);
 
 extern int check_add_feature(char *arg);
+extern void pr_check_features(const char *offset, const char *sep, int width);
 
 #endif /* __CR_CRTOOLS_H__ */