1 files changed, 86 insertions, 0 deletions
diff --git a/src/cli/cmd_help.c b/src/cli/cmd_help.c
new file mode 100644
index 000000000..7ee982242
--- /dev/null
+++ b/src/cli/cmd_help.c
@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include <stdio.h>
+#include <git2.h>
+#include "cli.h"
+#include "cmd.h"
+
+#define COMMAND_NAME "help"
+
+static char *command;
+static int show_help;
+
+static const cli_opt_spec opts[] = {
+	{ CLI_OPT_TYPE_SWITCH,   "help",     0, &show_help, 1,
+	  CLI_OPT_USAGE_HIDDEN,   NULL,     "display help about the help command" },
+	{ CLI_OPT_TYPE_ARG,      "command",  0, &command,   0,
+	  CLI_OPT_USAGE_DEFAULT, "command", "the command to show help for" },
+	{ 0 },
+};
+
+static int print_help(void)
+{
+	cli_opt_usage_fprint(stdout, PROGRAM_NAME, COMMAND_NAME, opts);
+	printf("\n");
+
+	printf("Display help information about %s.  If a command is specified, help\n", PROGRAM_NAME);
+	printf("about that command will be shown.  Otherwise, general information about\n");
+	printf("%s will be shown, including the commands available.\n", PROGRAM_NAME);
+
+	return 0;
+}
+
+static int print_commands(void)
+{
+	const cli_cmd_spec *cmd;
+
+	cli_opt_usage_fprint(stdout, PROGRAM_NAME, NULL, cli_common_opts);
+	printf("\n");
+
+	printf("These are the %s commands available:\n\n", PROGRAM_NAME);
+
+	for (cmd = cli_cmds; cmd->name; cmd++)
+		printf("   %-11s  %s\n", cmd->name, cmd->desc);
+
+	printf("\nSee '%s help <command>' for more information on a specific command.\n", PROGRAM_NAME);
+
+	return 0;
+}
+
+int cmd_help(int argc, char **argv)
+{
+	char *fake_args[2];
+	const cli_cmd_spec *cmd;
+	cli_opt invalid_opt;
+
+	if (cli_opt_parse(&invalid_opt, opts, argv + 1, argc - 1, CLI_OPT_PARSE_GNU))
+		return cli_opt_usage_error(COMMAND_NAME, opts, &invalid_opt);
+
+	/* Show the meta-help */
+	if (show_help)
+		return print_help();
+
+	/* We were not asked to show help for a specific command. */
+	if (!command)
+		return print_commands();
+
+	/*
+	 * If we were asked for help for a command (eg, `help <command>`),
+	 * delegate back to that command's `--help` option.  This lets
+	 * commands own their help.  Emulate the command-line arguments
+	 * that would invoke `<command> --help` and invoke that command.
+	 */
+	fake_args[0] = command;
+	fake_args[1] = "--help";
+
+	if ((cmd = cli_cmd_spec_byname(command)) == NULL)
+		return cli_error("'%s' is not a %s command. See '%s help'.",
+		                command, PROGRAM_NAME, PROGRAM_NAME);
+
+	return cmd->fn(2, fake_args);
+}