diff --git a/contrib/chg/chg.c b/contrib/chg/chg.c
--- a/contrib/chg/chg.c
+++ b/contrib/chg/chg.c
@@ -303,214 +303,7 @@ static void killcmdserver(const struct c
 	}
 }
 
-static pid_t pagerpid = 0;
-static pid_t peerpgid = 0;
-static pid_t peerpid = 0;
-
-static void forwardsignal(int sig)
-{
-	assert(peerpid > 0);
-	if (kill(peerpid, sig) < 0)
-		abortmsgerrno("cannot kill %d", peerpid);
-	debugmsg("forward signal %d", sig);
-}
-
-static void forwardsignaltogroup(int sig)
-{
-	/* prefer kill(-pgid, sig), fallback to pid if pgid is invalid */
-	pid_t killpid = peerpgid > 1 ? -peerpgid : peerpid;
-	if (kill(killpid, sig) < 0)
-		abortmsgerrno("cannot kill %d", killpid);
-	debugmsg("forward signal %d to %d", sig, killpid);
-}
-
-static void handlestopsignal(int sig)
-{
-	sigset_t unblockset, oldset;
-	struct sigaction sa, oldsa;
-	if (sigemptyset(&unblockset) < 0)
-		goto error;
-	if (sigaddset(&unblockset, sig) < 0)
-		goto error;
-	memset(&sa, 0, sizeof(sa));
-	sa.sa_handler = SIG_DFL;
-	sa.sa_flags = SA_RESTART;
-	if (sigemptyset(&sa.sa_mask) < 0)
-		goto error;
-
-	forwardsignal(sig);
-	if (raise(sig) < 0)  /* resend to self */
-		goto error;
-	if (sigaction(sig, &sa, &oldsa) < 0)
-		goto error;
-	if (sigprocmask(SIG_UNBLOCK, &unblockset, &oldset) < 0)
-		goto error;
-	/* resent signal will be handled before sigprocmask() returns */
-	if (sigprocmask(SIG_SETMASK, &oldset, NULL) < 0)
-		goto error;
-	if (sigaction(sig, &oldsa, NULL) < 0)
-		goto error;
-	return;
-
-error:
-	abortmsgerrno("failed to handle stop signal");
-}
-
-static void handlechildsignal(int sig UNUSED_)
-{
-	if (peerpid == 0 || pagerpid == 0)
-		return;
-	/* if pager exits, notify the server with SIGPIPE immediately.
-	 * otherwise the server won't get SIGPIPE if it does not write
-	 * anything. (issue5278) */
-	if (waitpid(pagerpid, NULL, WNOHANG) == pagerpid)
-		kill(peerpid, SIGPIPE);
-}
-
-static void setupsignalhandler(const hgclient_t *hgc)
-{
-	pid_t pid = hgc_peerpid(hgc);
-	if (pid <= 0)
-		return;
-	peerpid = pid;
-
-	pid_t pgid = hgc_peerpgid(hgc);
-	peerpgid = (pgid <= 1 ? 0 : pgid);
-
-	struct sigaction sa;
-	memset(&sa, 0, sizeof(sa));
-	sa.sa_handler = forwardsignaltogroup;
-	sa.sa_flags = SA_RESTART;
-	if (sigemptyset(&sa.sa_mask) < 0)
-		goto error;
-
-	if (sigaction(SIGHUP, &sa, NULL) < 0)
-		goto error;
-	if (sigaction(SIGINT, &sa, NULL) < 0)
-		goto error;
-
-	/* terminate frontend by double SIGTERM in case of server freeze */
-	sa.sa_handler = forwardsignal;
-	sa.sa_flags |= SA_RESETHAND;
-	if (sigaction(SIGTERM, &sa, NULL) < 0)
-		goto error;
-
-	/* notify the worker about window resize events */
-	sa.sa_flags = SA_RESTART;
-	if (sigaction(SIGWINCH, &sa, NULL) < 0)
-		goto error;
-	/* propagate job control requests to worker */
-	sa.sa_handler = forwardsignal;
-	sa.sa_flags = SA_RESTART;
-	if (sigaction(SIGCONT, &sa, NULL) < 0)
-		goto error;
-	sa.sa_handler = handlestopsignal;
-	sa.sa_flags = SA_RESTART;
-	if (sigaction(SIGTSTP, &sa, NULL) < 0)
-		goto error;
-	/* get notified when pager exits */
-	sa.sa_handler = handlechildsignal;
-	sa.sa_flags = SA_RESTART;
-	if (sigaction(SIGCHLD, &sa, NULL) < 0)
-		goto error;
-
-	return;
-
-error:
-	abortmsgerrno("failed to set up signal handlers");
-}
-
-static void restoresignalhandler()
-{
-	struct sigaction sa;
-	memset(&sa, 0, sizeof(sa));
-	sa.sa_handler = SIG_DFL;
-	sa.sa_flags = SA_RESTART;
-	if (sigemptyset(&sa.sa_mask) < 0)
-		goto error;
-
-	if (sigaction(SIGHUP, &sa, NULL) < 0)
-		goto error;
-	if (sigaction(SIGTERM, &sa, NULL) < 0)
-		goto error;
-	if (sigaction(SIGWINCH, &sa, NULL) < 0)
-		goto error;
-	if (sigaction(SIGCONT, &sa, NULL) < 0)
-		goto error;
-	if (sigaction(SIGTSTP, &sa, NULL) < 0)
-		goto error;
-	if (sigaction(SIGCHLD, &sa, NULL) < 0)
-		goto error;
-
-	/* ignore Ctrl+C while shutting down to make pager exits cleanly */
-	sa.sa_handler = SIG_IGN;
-	if (sigaction(SIGINT, &sa, NULL) < 0)
-		goto error;
-
-	peerpid = 0;
-	return;
-
-error:
-	abortmsgerrno("failed to restore signal handlers");
-}
-
-/* This implementation is based on hgext/pager.py (post 369741ef7253)
- * Return 0 if pager is not started, or pid of the pager */
-static pid_t setuppager(hgclient_t *hgc, const char *const args[],
-		       size_t argsize)
-{
-	const char *pagercmd = hgc_getpager(hgc, args, argsize);
-	if (!pagercmd)
-		return 0;
-
-	int pipefds[2];
-	if (pipe(pipefds) < 0)
-		return 0;
-	pid_t pid = fork();
-	if (pid < 0)
-		goto error;
-	if (pid > 0) {
-		close(pipefds[0]);
-		if (dup2(pipefds[1], fileno(stdout)) < 0)
-			goto error;
-		if (isatty(fileno(stderr))) {
-			if (dup2(pipefds[1], fileno(stderr)) < 0)
-				goto error;
-		}
-		close(pipefds[1]);
-		hgc_attachio(hgc);  /* reattach to pager */
-		return pid;
-	} else {
-		dup2(pipefds[0], fileno(stdin));
-		close(pipefds[0]);
-		close(pipefds[1]);
-
-		int r = execlp("/bin/sh", "/bin/sh", "-c", pagercmd, NULL);
-		if (r < 0) {
-			abortmsgerrno("cannot start pager '%s'", pagercmd);
-		}
-		return 0;
-	}
-
-error:
-	close(pipefds[0]);
-	close(pipefds[1]);
-	abortmsgerrno("failed to prepare pager");
-	return 0;
-}
-
-static void waitpager(pid_t pid)
-{
-	/* close output streams to notify the pager its input ends */
-	fclose(stdout);
-	fclose(stderr);
-	while (1) {
-		pid_t ret = waitpid(pid, NULL, 0);
-		if (ret == -1 && errno == EINTR)
-			continue;
-		break;
-	}
-}
+#include "procutil.c"
 
 /* Run instructions sent from the server like unlink and set redirect path
  * Return 1 if reconnect is needed, otherwise 0 */
diff --git a/contrib/chg/chg.c b/contrib/chg/procutil.c
copy from contrib/chg/chg.c
copy to contrib/chg/procutil.c
--- a/contrib/chg/chg.c
+++ b/contrib/chg/procutil.c
@@ -1,5 +1,5 @@
 /*
- * A fast client for Mercurial command server
+ * Utilities about process handling - signal and subprocess (ex. pager)
  *
  * Copyright (c) 2011 Yuya Nishihara <yuya@tcha.org>
  *
@@ -7,302 +7,6 @@
  * GNU General Public License version 2 or any later version.
  */
 
-#include <assert.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <signal.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/file.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <sys/un.h>
-#include <sys/wait.h>
-#include <time.h>
-#include <unistd.h>
-
-#include "hgclient.h"
-#include "util.h"
-
-#ifndef PATH_MAX
-#define PATH_MAX 4096
-#endif
-
-struct cmdserveropts {
-	char sockname[PATH_MAX];
-	char initsockname[PATH_MAX];
-	char redirectsockname[PATH_MAX];
-	size_t argsize;
-	const char **args;
-};
-
-static void initcmdserveropts(struct cmdserveropts *opts) {
-	memset(opts, 0, sizeof(struct cmdserveropts));
-}
-
-static void freecmdserveropts(struct cmdserveropts *opts) {
-	free(opts->args);
-	opts->args = NULL;
-	opts->argsize = 0;
-}
-
-/*
- * Test if an argument is a sensitive flag that should be passed to the server.
- * Return 0 if not, otherwise the number of arguments starting from the current
- * one that should be passed to the server.
- */
-static size_t testsensitiveflag(const char *arg)
-{
-	static const struct {
-		const char *name;
-		size_t narg;
-	} flags[] = {
-		{"--config", 1},
-		{"--cwd", 1},
-		{"--repo", 1},
-		{"--repository", 1},
-		{"--traceback", 0},
-		{"-R", 1},
-	};
-	size_t i;
-	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); ++i) {
-		size_t len = strlen(flags[i].name);
-		size_t narg = flags[i].narg;
-		if (memcmp(arg, flags[i].name, len) == 0) {
-			if (arg[len] == '\0') {
-				/* --flag (value) */
-				return narg + 1;
-			} else if (arg[len] == '=' && narg > 0) {
-				/* --flag=value */
-				return 1;
-			} else if (flags[i].name[1] != '-') {
-				/* short flag */
-				return 1;
-			}
-		}
-	}
-	return 0;
-}
-
-/*
- * Parse argv[] and put sensitive flags to opts->args
- */
-static void setcmdserverargs(struct cmdserveropts *opts,
-			     int argc, const char *argv[])
-{
-	size_t i, step;
-	opts->argsize = 0;
-	for (i = 0, step = 1; i < (size_t)argc; i += step, step = 1) {
-		if (!argv[i])
-			continue;  /* pass clang-analyse */
-		if (strcmp(argv[i], "--") == 0)
-			break;
-		size_t n = testsensitiveflag(argv[i]);
-		if (n == 0 || i + n > (size_t)argc)
-			continue;
-		opts->args = reallocx(opts->args,
-				      (n + opts->argsize) * sizeof(char *));
-		memcpy(opts->args + opts->argsize, argv + i,
-		       sizeof(char *) * n);
-		opts->argsize += n;
-		step = n;
-	}
-}
-
-static void preparesockdir(const char *sockdir)
-{
-	int r;
-	r = mkdir(sockdir, 0700);
-	if (r < 0 && errno != EEXIST)
-		abortmsgerrno("cannot create sockdir %s", sockdir);
-
-	struct stat st;
-	r = lstat(sockdir, &st);
-	if (r < 0)
-		abortmsgerrno("cannot stat %s", sockdir);
-	if (!S_ISDIR(st.st_mode))
-		abortmsg("cannot create sockdir %s (file exists)", sockdir);
-	if (st.st_uid != geteuid() || st.st_mode & 0077)
-		abortmsg("insecure sockdir %s", sockdir);
-}
-
-static void getdefaultsockdir(char sockdir[], size_t size)
-{
-	/* by default, put socket file in secure directory
-	 * (${XDG_RUNTIME_DIR}/chg, or /${TMPDIR:-tmp}/chg$UID)
-	 * (permission of socket file may be ignored on some Unices) */
-	const char *runtimedir = getenv("XDG_RUNTIME_DIR");
-	int r;
-	if (runtimedir) {
-		r = snprintf(sockdir, size, "%s/chg", runtimedir);
-	} else {
-		const char *tmpdir = getenv("TMPDIR");
-		if (!tmpdir)
-			tmpdir = "/tmp";
-		r = snprintf(sockdir, size, "%s/chg%d", tmpdir, geteuid());
-	}
-	if (r < 0 || (size_t)r >= size)
-		abortmsg("too long TMPDIR (r = %d)", r);
-}
-
-static void setcmdserveropts(struct cmdserveropts *opts)
-{
-	int r;
-	char sockdir[PATH_MAX];
-	const char *envsockname = getenv("CHGSOCKNAME");
-	if (!envsockname) {
-		getdefaultsockdir(sockdir, sizeof(sockdir));
-		preparesockdir(sockdir);
-	}
-
-	const char *basename = (envsockname) ? envsockname : sockdir;
-	const char *sockfmt = (envsockname) ? "%s" : "%s/server";
-	r = snprintf(opts->sockname, sizeof(opts->sockname), sockfmt, basename);
-	if (r < 0 || (size_t)r >= sizeof(opts->sockname))
-		abortmsg("too long TMPDIR or CHGSOCKNAME (r = %d)", r);
-	r = snprintf(opts->initsockname, sizeof(opts->initsockname),
-			"%s.%u", opts->sockname, (unsigned)getpid());
-	if (r < 0 || (size_t)r >= sizeof(opts->initsockname))
-		abortmsg("too long TMPDIR or CHGSOCKNAME (r = %d)", r);
-}
-
-static const char *gethgcmd(void)
-{
-	static const char *hgcmd = NULL;
-	if (!hgcmd) {
-		hgcmd = getenv("CHGHG");
-		if (!hgcmd || hgcmd[0] == '\0')
-			hgcmd = getenv("HG");
-		if (!hgcmd || hgcmd[0] == '\0')
-#ifdef HGPATH
-			hgcmd = (HGPATH);
-#else
-			hgcmd = "hg";
-#endif
-	}
-	return hgcmd;
-}
-
-static void execcmdserver(const struct cmdserveropts *opts)
-{
-	const char *hgcmd = gethgcmd();
-
-	const char *baseargv[] = {
-		hgcmd,
-		"serve",
-		"--cmdserver", "chgunix",
-		"--address", opts->initsockname,
-		"--daemon-postexec", "chdir:/",
-	};
-	size_t baseargvsize = sizeof(baseargv) / sizeof(baseargv[0]);
-	size_t argsize = baseargvsize + opts->argsize + 1;
-
-	const char **argv = mallocx(sizeof(char *) * argsize);
-	memcpy(argv, baseargv, sizeof(baseargv));
-	memcpy(argv + baseargvsize, opts->args, sizeof(char *) * opts->argsize);
-	argv[argsize - 1] = NULL;
-
-	if (putenv("CHGINTERNALMARK=") != 0)
-		abortmsgerrno("failed to putenv");
-	if (execvp(hgcmd, (char **)argv) < 0)
-		abortmsgerrno("failed to exec cmdserver");
-	free(argv);
-}
-
-/* Retry until we can connect to the server. Give up after some time. */
-static hgclient_t *retryconnectcmdserver(struct cmdserveropts *opts, pid_t pid)
-{
-	static const struct timespec sleepreq = {0, 10 * 1000000};
-	int pst = 0;
-
-	debugmsg("try connect to %s repeatedly", opts->initsockname);
-
-	unsigned int timeoutsec = 60;  /* default: 60 seconds */
-	const char *timeoutenv = getenv("CHGTIMEOUT");
-	if (timeoutenv)
-		sscanf(timeoutenv, "%u", &timeoutsec);
-
-	for (unsigned int i = 0; !timeoutsec || i < timeoutsec * 100; i++) {
-		hgclient_t *hgc = hgc_open(opts->initsockname);
-		if (hgc) {
-			debugmsg("rename %s to %s", opts->initsockname,
-					opts->sockname);
-			int r = rename(opts->initsockname, opts->sockname);
-			if (r != 0)
-				abortmsgerrno("cannot rename");
-			return hgc;
-		}
-
-		if (pid > 0) {
-			/* collect zombie if child process fails to start */
-			int r = waitpid(pid, &pst, WNOHANG);
-			if (r != 0)
-				goto cleanup;
-		}
-
-		nanosleep(&sleepreq, NULL);
-	}
-
-	abortmsg("timed out waiting for cmdserver %s", opts->initsockname);
-	return NULL;
-
-cleanup:
-	if (WIFEXITED(pst)) {
-		if (WEXITSTATUS(pst) == 0)
-			abortmsg("could not connect to cmdserver "
-				 "(exited with status 0)");
-		debugmsg("cmdserver exited with status %d", WEXITSTATUS(pst));
-		exit(WEXITSTATUS(pst));
-	} else if (WIFSIGNALED(pst)) {
-		abortmsg("cmdserver killed by signal %d", WTERMSIG(pst));
-	} else {
-		abortmsg("error while waiting for cmdserver");
-	}
-	return NULL;
-}
-
-/* Connect to a cmdserver. Will start a new server on demand. */
-static hgclient_t *connectcmdserver(struct cmdserveropts *opts)
-{
-	const char *sockname = opts->redirectsockname[0] ?
-		opts->redirectsockname : opts->sockname;
-	debugmsg("try connect to %s", sockname);
-	hgclient_t *hgc = hgc_open(sockname);
-	if (hgc)
-		return hgc;
-
-	/* prevent us from being connected to an outdated server: we were
-	 * told by a server to redirect to opts->redirectsockname and that
-	 * address does not work. we do not want to connect to the server
-	 * again because it will probably tell us the same thing. */
-	if (sockname == opts->redirectsockname)
-		unlink(opts->sockname);
-
-	debugmsg("start cmdserver at %s", opts->initsockname);
-
-	pid_t pid = fork();
-	if (pid < 0)
-		abortmsg("failed to fork cmdserver process");
-	if (pid == 0) {
-		execcmdserver(opts);
-	} else {
-		hgc = retryconnectcmdserver(opts, pid);
-	}
-
-	return hgc;
-}
-
-static void killcmdserver(const struct cmdserveropts *opts)
-{
-	/* resolve config hash */
-	char *resolvedpath = realpath(opts->sockname, NULL);
-	if (resolvedpath) {
-		unlink(resolvedpath);
-		free(resolvedpath);
-	}
-}
-
 static pid_t pagerpid = 0;
 static pid_t peerpgid = 0;
 static pid_t peerpid = 0;
@@ -511,139 +215,3 @@ static void waitpager(pid_t pid)
 		break;
 	}
 }
-
-/* Run instructions sent from the server like unlink and set redirect path
- * Return 1 if reconnect is needed, otherwise 0 */
-static int runinstructions(struct cmdserveropts *opts, const char **insts)
-{
-	int needreconnect = 0;
-	if (!insts)
-		return needreconnect;
-
-	assert(insts);
-	opts->redirectsockname[0] = '\0';
-	const char **pinst;
-	for (pinst = insts; *pinst; pinst++) {
-		debugmsg("instruction: %s", *pinst);
-		if (strncmp(*pinst, "unlink ", 7) == 0) {
-			unlink(*pinst + 7);
-		} else if (strncmp(*pinst, "redirect ", 9) == 0) {
-			int r = snprintf(opts->redirectsockname,
-					 sizeof(opts->redirectsockname),
-					 "%s", *pinst + 9);
-			if (r < 0 || r >= (int)sizeof(opts->redirectsockname))
-				abortmsg("redirect path is too long (%d)", r);
-			needreconnect = 1;
-		} else if (strncmp(*pinst, "exit ", 5) == 0) {
-			int n = 0;
-			if (sscanf(*pinst + 5, "%d", &n) != 1)
-				abortmsg("cannot read the exit code");
-			exit(n);
-		} else if (strcmp(*pinst, "reconnect") == 0) {
-			needreconnect = 1;
-		} else {
-			abortmsg("unknown instruction: %s", *pinst);
-		}
-	}
-	return needreconnect;
-}
-
-/*
- * Test whether the command is unsupported or not. This is not designed to
- * cover all cases. But it's fast, does not depend on the server and does
- * not return false positives.
- */
-static int isunsupported(int argc, const char *argv[])
-{
-	enum {
-		SERVE = 1,
-		DAEMON = 2,
-		SERVEDAEMON = SERVE | DAEMON,
-		TIME = 4,
-	};
-	unsigned int state = 0;
-	int i;
-	for (i = 0; i < argc; ++i) {
-		if (strcmp(argv[i], "--") == 0)
-			break;
-		if (i == 0 && strcmp("serve", argv[i]) == 0)
-			state |= SERVE;
-		else if (strcmp("-d", argv[i]) == 0 ||
-			 strcmp("--daemon", argv[i]) == 0)
-			state |= DAEMON;
-		else if (strcmp("--time", argv[i]) == 0)
-			state |= TIME;
-	}
-	return (state & TIME) == TIME ||
-	       (state & SERVEDAEMON) == SERVEDAEMON;
-}
-
-static void execoriginalhg(const char *argv[])
-{
-	debugmsg("execute original hg");
-	if (execvp(gethgcmd(), (char **)argv) < 0)
-		abortmsgerrno("failed to exec original hg");
-}
-
-int main(int argc, const char *argv[], const char *envp[])
-{
-	if (getenv("CHGDEBUG"))
-		enabledebugmsg();
-
-	if (!getenv("HGPLAIN") && isatty(fileno(stderr)))
-		enablecolor();
-
-	if (getenv("CHGINTERNALMARK"))
-		abortmsg("chg started by chg detected.\n"
-			 "Please make sure ${HG:-hg} is not a symlink or "
-			 "wrapper to chg. Alternatively, set $CHGHG to the "
-			 "path of real hg.");
-
-	if (isunsupported(argc - 1, argv + 1))
-		execoriginalhg(argv);
-
-	struct cmdserveropts opts;
-	initcmdserveropts(&opts);
-	setcmdserveropts(&opts);
-	setcmdserverargs(&opts, argc, argv);
-
-	if (argc == 2) {
-		if (strcmp(argv[1], "--kill-chg-daemon") == 0) {
-			killcmdserver(&opts);
-			return 0;
-		}
-	}
-
-	hgclient_t *hgc;
-	size_t retry = 0;
-	while (1) {
-		hgc = connectcmdserver(&opts);
-		if (!hgc)
-			abortmsg("cannot open hg client");
-		hgc_setenv(hgc, envp);
-		const char **insts = hgc_validate(hgc, argv + 1, argc - 1);
-		int needreconnect = runinstructions(&opts, insts);
-		free(insts);
-		if (!needreconnect)
-			break;
-		hgc_close(hgc);
-		if (++retry > 10)
-			abortmsg("too many redirections.\n"
-				 "Please make sure %s is not a wrapper which "
-				 "changes sensitive environment variables "
-				 "before executing hg. If you have to use a "
-				 "wrapper, wrap chg instead of hg.",
-				 gethgcmd());
-	}
-
-	setupsignalhandler(hgc);
-	pagerpid = setuppager(hgc, argv + 1, argc - 1);
-	int exitcode = hgc_runcommand(hgc, argv + 1, argc - 1);
-	restoresignalhandler();
-	hgc_close(hgc);
-	freecmdserveropts(&opts);
-	if (pagerpid)
-		waitpager(pagerpid);
-
-	return exitcode;
-}