RFC: [PATCH] ignore SIGINT&QUIT while waiting for external command

[Dmitry Potapov <dpotapov@gmail.com>]

Before git 1.6.4, we used execvp to run external git dashed commands,
thus git did not return until this command is finished. With switching to
run_command (which was necessary to fix a pager issue; see d8e96fd86d4),
CTRL-C could cause that git returned before than the git dashed command is
finished.

The solution is to disable SIGINT and SIGQUIT as it is normally done by
system(). Disabling these signals is done only when silent_exec_failure
is set, which means that the current process is used as a proxy to run
another command.

Signed-off-by: Dmitry Potapov <dpotapov@gmail.com>
---
 run-command.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/run-command.c b/run-command.c
index 2a1041e..14af035 100644
--- a/run-command.c
+++ b/run-command.c
@@ -93,6 +93,10 @@ static inline void set_cloexec(int fd)
 		fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 }
 
+#ifndef WIN32
+static sighandler_t sigint, sigquit;
+#endif
+
 static int wait_or_whine(pid_t pid, const char *argv0, int silent_exec_failure)
 {
 	int status, code = -1;
@@ -102,6 +106,13 @@ static int wait_or_whine(pid_t pid, const char *argv0, int silent_exec_failure)
 	while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 		;	/* nothing */
 
+#ifndef WIN32
+	if (silent_exec_failure) {
+		/* Restore signal handlers */
+		signal(SIGINT, sigint);
+		signal(SIGQUIT, sigquit);
+	}
+#endif
 	if (waiting < 0) {
 		failed_errno = errno;
 		error("waitpid for %s failed: %s", argv0, strerror(errno));
@@ -202,8 +213,16 @@ fail_pipe:
 		notify_pipe[0] = notify_pipe[1] = -1;
 
 	fflush(NULL);
+	if (cmd->silent_exec_failure) {
+		sigint = signal(SIGINT, SIG_IGN);
+		sigquit = signal(SIGQUIT, SIG_IGN);
+	}
 	cmd->pid = fork();
 	if (!cmd->pid) {
+		if (cmd->silent_exec_failure) {
+			signal(SIGINT, sigint);
+			signal(SIGQUIT, sigquit);
+		}
 		/*
 		 * Redirect the channel to write syscall error messages to
 		 * before redirecting the process's stderr so that all die()
-- 
1.7.3.1