yanglint FEATURE initial version of yanglint(1)

Source codes are mostly taken from libyang 1.0 and slightly modified for
libyang 2.0. A lot of functionality is still missing since it is not yet
provided by libyang 2.0
diff --git a/tools/lint/main.c b/tools/lint/main.c
new file mode 100644
index 0000000..6b257da
--- /dev/null
+++ b/tools/lint/main.c
@@ -0,0 +1,111 @@
+/**
+ * @file main.c
+ * @author Radek Krejci <rkrejci@cesnet.cz>
+ * @brief libyang's yanglint tool
+ *
+ * Copyright (c) 2015-2017 CESNET, z.s.p.o.
+ *
+ * This source code is licensed under BSD 3-Clause License (the "License").
+ * You may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://opensource.org/licenses/BSD-3-Clause
+ */
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "commands.h"
+#include "configuration.h"
+#include "completion.h"
+#include "./linenoise/linenoise.h"
+#include "libyang.h"
+
+int done;
+struct ly_ctx *ctx = NULL;
+
+/* main_ni.c */
+int main_ni(int argc, char *argv[]);
+
+int
+main(int argc, char* argv[])
+{
+    char *cmd, *cmdline, *cmdstart;
+    int i, j;
+
+    if (argc > 1) {
+        /* run in non-interactive mode */
+        return main_ni(argc, argv);
+    }
+
+    /* continue in interactive mode */
+    linenoiseSetCompletionCallback(complete_cmd);
+    load_config();
+
+    if (ly_ctx_new(NULL, 0, &ctx)) {
+        fprintf(stderr, "Failed to create context.\n");
+        return 1;
+    }
+
+    while (!done) {
+        /* get the command from user */
+        cmdline = linenoise(PROMPT);
+
+        /* EOF -> exit */
+        if (cmdline == NULL) {
+            done = 1;
+            cmdline = strdup("quit");
+        }
+
+        /* empty line -> wait for another command */
+        if (*cmdline == '\0') {
+            free(cmdline);
+            continue;
+        }
+
+        /* isolate the command word. */
+        for (i = 0; cmdline[i] && (cmdline[i] == ' '); i++);
+        cmdstart = cmdline + i;
+        for (j = 0; cmdline[i] && (cmdline[i] != ' '); i++, j++);
+        cmd = strndup(cmdstart, j);
+
+        /* parse the command line */
+        for (i = 0; commands[i].name; i++) {
+            if (strcmp(cmd, commands[i].name) == 0) {
+                break;
+            }
+        }
+
+        /* execute the command if any valid specified */
+        if (commands[i].name) {
+            /* display help */
+            if ((strchr(cmdstart, ' ') != NULL) && ((strncmp(strchr(cmdstart, ' ')+1, "-h", 2) == 0)
+                    || (strncmp(strchr(cmdstart, ' ')+1, "--help", 6) == 0))) {
+                if (commands[i].help_func != NULL) {
+                    commands[i].help_func();
+                } else {
+                    printf("%s\n", commands[i].helpstring);
+                }
+            } else {
+                commands[i].func((const char *)cmdstart);
+            }
+        } else {
+            /* if unknown command specified, tell it to user */
+            fprintf(stderr, "%s: no such command, type 'help' for more information.\n", cmd);
+        }
+        linenoiseHistoryAdd(cmdline);
+
+        free(cmd);
+        free(cmdline);
+    }
+
+    store_config();
+    ly_ctx_destroy(ctx, NULL);
+
+    return 0;
+}