--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/contrib/chg/util.c	Sun Jan 03 12:39:27 2016 +0900
@@ -0,0 +1,121 @@
+/*
+ * Utility functions
+ *
+ * Copyright (c) 2011 Yuya Nishihara <yuya@tcha.org>
+ *
+ * This software may be used and distributed according to the terms of the
+ * GNU General Public License version 2 or any later version.
+ */
+
+#include <signal.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "util.h"
+
+void abortmsg(const char *fmt, ...)
+{
+	va_list args;
+	va_start(args, fmt);
+	fputs("\033[1;31mchg: abort: ", stderr);
+	vfprintf(stderr, fmt, args);
+	fputs("\033[m\n", stderr);
+	va_end(args);
+
+	exit(255);
+}
+
+static int debugmsgenabled = 0;
+
+void enabledebugmsg(void)
+{
+	debugmsgenabled = 1;
+}
+
+void debugmsg(const char *fmt, ...)
+{
+	if (!debugmsgenabled)
+		return;
+
+	va_list args;
+	va_start(args, fmt);
+	fputs("\033[1;30mchg: debug: ", stderr);
+	vfprintf(stderr, fmt, args);
+	fputs("\033[m\n", stderr);
+	va_end(args);
+}
+
+/*
+ * Execute a shell command in mostly the same manner as system(), with the
+ * give environment variables, after chdir to the given cwd. Returns a status
+ * code compatible with the Python subprocess module.
+ */
+int runshellcmd(const char *cmd, const char *envp[], const char *cwd)
+{
+	enum { F_SIGINT = 1, F_SIGQUIT = 2, F_SIGMASK = 4, F_WAITPID = 8 };
+	unsigned int doneflags = 0;
+	int status = 0;
+	struct sigaction newsa, oldsaint, oldsaquit;
+	sigset_t oldmask;
+
+	/* block or mask signals just as system() does */
+	newsa.sa_handler = SIG_IGN;
+	newsa.sa_flags = 0;
+	if (sigemptyset(&newsa.sa_mask) < 0)
+		goto done;
+	if (sigaction(SIGINT, &newsa, &oldsaint) < 0)
+		goto done;
+	doneflags |= F_SIGINT;
+	if (sigaction(SIGQUIT, &newsa, &oldsaquit) < 0)
+		goto done;
+	doneflags |= F_SIGQUIT;
+
+	if (sigaddset(&newsa.sa_mask, SIGCHLD) < 0)
+		goto done;
+	if (sigprocmask(SIG_BLOCK, &newsa.sa_mask, &oldmask) < 0)
+		goto done;
+	doneflags |= F_SIGMASK;
+
+	pid_t pid = fork();
+	if (pid < 0)
+		goto done;
+	if (pid == 0) {
+		sigaction(SIGINT, &oldsaint, NULL);
+		sigaction(SIGQUIT, &oldsaquit, NULL);
+		sigprocmask(SIG_SETMASK, &oldmask, NULL);
+		if (cwd && chdir(cwd) < 0)
+			_exit(127);
+		const char *argv[] = {"sh", "-c", cmd, NULL};
+		if (envp) {
+			execve("/bin/sh", (char **)argv, (char **)envp);
+		} else {
+			execv("/bin/sh", (char **)argv);
+		}
+		_exit(127);
+	} else {
+		if (waitpid(pid, &status, 0) < 0)
+			goto done;
+		doneflags |= F_WAITPID;
+	}
+
+done:
+	if (doneflags & F_SIGINT)
+		sigaction(SIGINT, &oldsaint, NULL);
+	if (doneflags & F_SIGQUIT)
+		sigaction(SIGQUIT, &oldsaquit, NULL);
+	if (doneflags & F_SIGMASK)
+		sigprocmask(SIG_SETMASK, &oldmask, NULL);
+
+	/* no way to report other errors, use 127 (= shell termination) */
+	if (!(doneflags & F_WAITPID))
+		return 127;
+	if (WIFEXITED(status))
+		return WEXITSTATUS(status);
+	if (WIFSIGNALED(status))
+		return -WTERMSIG(status);
+	return 127;
+}