patch, 4 partsgit-shell-commands: Add a help command

diff --git a/shell.c b/shell.c
index e4864e0..fe1fe73 100644
--- a/shell.c
+++ b/shell.c
@@ -3,6 +3,8 @@
 #include "exec_cmd.h"
 #include "strbuf.h"
 
+#define COMMAND_DIR "git-shell-commands"
+
 static int do_generic_cmd(const char *me, char *arg)
 {
 	const char *my_argv[4];
@@ -33,6 +35,20 @@ static int do_cvs_cmd(const char *me, char *arg)
 	return execv_git_cmd(cvsserver_argv);
 }
 
+static int is_valid_cmd_name(const char *cmd)
+{
+	/* Test command contains no . or / characters */
+	return cmd[strcspn(cmd, "./")] == '\0';
+}
+
+static char *make_cmd(const char *prog)
+{
+	char *prefix = xmalloc((strlen(prog) + strlen(COMMAND_DIR) + 2) * sizeof(char));
+	strcpy(prefix, COMMAND_DIR);
+	strcat(prefix, "/");
+	strcat(prefix, prog);
+	return prefix;
+}
 
 static struct commands {
 	const char *name;
@@ -48,6 +64,8 @@ static struct commands {
 int main(int argc, char **argv)
 {
 	char *prog;
+	char *prog_cpy;
+	const char **user_argv;
 	struct commands *cmd;
 	int devnull_fd;
 
@@ -77,6 +95,7 @@ int main(int argc, char **argv)
 		die("What do you think I am? A shell?");
 
 	prog = argv[2];
+	prog_cpy = xstrdup(prog);
 	if (!strncmp(prog, "git", 3) && isspace(prog[3]))
 		/* Accept "git foo" as if the caller said "git-foo". */
 		prog[3] = '-';
@@ -99,5 +118,25 @@ int main(int argc, char **argv)
 		}
 		exit(cmd->exec(cmd->name, arg));
 	}
-	die("unrecognized command '%s'", prog);
+
+	if (split_cmdline(prog, &user_argv) != -1) {
+		if (is_valid_cmd_name(user_argv[0])) {
+			prog  = make_cmd(user_argv[0]);
+			user_argv[0] = prog;
+			execv(user_argv[0], (char *const *) user_argv);
+			free(prog);
+		}
+		free(user_argv);
+		/*
+		 * split_cmdline modifies its argument in-place, so 'prog' now
+		 * holds the actual command name
+		 */
+		die("unrecognized command '%s'", prog_cpy);
+	} else {
+		/*
+		 * split_cmdline has clobbered prog and printed an
+		 * error message, so print the original
+		 */
+		die("invalid command format '%s'", prog_cpy);
+	}
 }

diff --git a/contrib/git-shell-commands/list b/contrib/git-shell-commands/list
new file mode 100755
index 0000000..cd8b15a
--- /dev/null
+++ b/contrib/git-shell-commands/list
@@ -0,0 +1,5 @@
+#!/bin/sh
+set -eu
+
+print_if_bare_repo='[ "$(git --git-dir="$1" rev-parse --is-bare-repository)" = true ] && echo "${1#./}"'
+find -type d -name "*.git" -exec sh -c "$print_if_bare_repo" -- \{} \; -prune

diff --git a/contrib/git-shell-commands/help b/contrib/git-shell-commands/help
new file mode 100755
index 0000000..19d5277
--- /dev/null
+++ b/contrib/git-shell-commands/help
@@ -0,0 +1,18 @@
+#!/bin/sh
+
+set -eu
+
+if tty -s; then
+    echo "Run 'help' for help, or 'exit' to leave.  Available commands:"
+else
+    echo "Run 'help' for help.  Available commands:"
+fi
+
+cd "$(dirname "$0")"
+
+for cmd in *; do
+    case "$cmd" in
+	help) ;;
+	*) [ -f "$cmd" ] && [ -x "$cmd" ] && echo "$cmd" ;;
+    esac
+done

diff --git a/shell.c b/shell.c
index fe1fe73..142d201 100644
--- a/shell.c
+++ b/shell.c
@@ -2,8 +2,10 @@
 #include "quote.h"
 #include "exec_cmd.h"
 #include "strbuf.h"
+#include "run-command.h"
 
 #define COMMAND_DIR "git-shell-commands"
+#define HELP_COMMAND COMMAND_DIR "/help"
 
 static int do_generic_cmd(const char *me, char *arg)
 {
@@ -50,6 +52,56 @@ static char *make_cmd(const char *prog)
 	return prefix;
 }
 
+static void run_shell(void)
+{
+	int done = 0;
+	static const char *help_argv[] = { HELP_COMMAND, NULL };
+	/* Print help if enabled */
+	run_command_v_opt(help_argv, RUN_SILENT_EXEC_FAILURE);
+
+	do {
+		struct strbuf line = STRBUF_INIT;
+		const char *prog;
+		char *full_cmd;
+		char *rawargs;
+		const char **argv;
+		int code;
+
+		fprintf(stderr, "git> ");
+		if (strbuf_getline(&line, stdin, '\n') == EOF) {
+			fprintf(stderr, "\n");
+			strbuf_release(&line);
+			break;
+		}
+		strbuf_trim(&line);
+		rawargs = strbuf_detach(&line, NULL);
+		if (split_cmdline(rawargs, &argv) == -1) {
+			free(rawargs);
+			continue;
+		}
+
+		prog = argv[0];
+		if (!strcmp(prog, "")) {
+		} else if (!strcmp(prog, "quit") || !strcmp(prog, "logout") ||
+			   !strcmp(prog, "exit") || !strcmp(prog, "bye")) {
+			done = 1;
+		} else if (is_valid_cmd_name(prog)) {
+			full_cmd = make_cmd(prog);
+			argv[0] = full_cmd;
+			code = run_command_v_opt(argv, RUN_SILENT_EXEC_FAILURE);
+			if (code == -1 && errno == ENOENT) {
+				fprintf(stderr, "unrecognized command '%s'\n", prog);
+			}
+			free(full_cmd);
+		} else {
+			fprintf(stderr, "invalid command format '%s'\n", prog);
+		}
+
+		free(argv);
+		free(rawargs);
+	} while (!done);
+}
+
 static struct commands {
 	const char *name;
 	int (*exec)(const char *me, char *arg);
@@ -84,15 +136,26 @@ int main(int argc, char **argv)
 	/*
 	 * Special hack to pretend to be a CVS server
 	 */
-	if (argc == 2 && !strcmp(argv[1], "cvs server"))
+	if (argc == 2 && !strcmp(argv[1], "cvs server")) {
 		argv--;
-
+	}
 	/*
-	 * We do not accept anything but "-c" followed by "cmd arg",
-	 * where "cmd" is a very limited subset of git commands.
+	 * Allow the user to run an interactive shell
 	 */
-	else if (argc != 3 || strcmp(argv[1], "-c"))
-		die("What do you think I am? A shell?");
+	else if (argc == 1) {
+		if (access(COMMAND_DIR, R_OK | X_OK) == -1)
+			die("Sorry, the interactive git-shell is not enabled");
+		run_shell();
+		exit(0);
+	}
+	/*
+	 * We do not accept any other modes except "-c" followed by
+	 * "cmd arg", where "cmd" is a very limited subset of git
+	 * commands or a command in the COMMAND_DIR
+	 */
+	else if (argc != 3 || strcmp(argv[1], "-c")) {
+		die("Run with no arguments or with -c cmd");
+	}
 
 	prog = argv[2];
 	prog_cpy = xstrdup(prog);