Teach run-command about stdout redirection

Some potential callers of the run_command family of functions need
to control not only the stdin redirection of the child, but also
the stdout redirection of the child.  This can now be setup much
like the already existing stdin redirection.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/run-command.c b/run-command.c
index bef9775..d20a6ef 100644
--- a/run-command.c
+++ b/run-command.c
@@ -11,7 +11,8 @@
 int start_command(struct child_process *cmd)
 {
 	int need_in = !cmd->no_stdin && cmd->in < 0;
-	int fdin[2];
+	int need_out = !cmd->stdout_to_stderr && cmd->out < 0;
+	int fdin[2], fdout[2];
 
 	if (need_in) {
 		if (pipe(fdin) < 0)
@@ -20,10 +21,22 @@
 		cmd->close_in = 1;
 	}
 
+	if (need_out) {
+		if (pipe(fdout) < 0) {
+			if (need_in)
+				close_pair(fdin);
+			return -ERR_RUN_COMMAND_PIPE;
+		}
+		cmd->out = fdout[0];
+		cmd->close_out = 1;
+	}
+
 	cmd->pid = fork();
 	if (cmd->pid < 0) {
 		if (need_in)
 			close_pair(fdin);
+		if (need_out)
+			close_pair(fdout);
 		return -ERR_RUN_COMMAND_FORK;
 	}
 
@@ -42,6 +55,14 @@
 
 		if (cmd->stdout_to_stderr)
 			dup2(2, 1);
+		else if (need_out) {
+			dup2(fdout[1], 1);
+			close_pair(fdout);
+		} else if (cmd->out > 1) {
+			dup2(cmd->out, 1);
+			close(cmd->out);
+		}
+
 		if (cmd->git_cmd) {
 			execv_git_cmd(cmd->argv);
 		} else {
@@ -55,6 +76,11 @@
 	else if (cmd->in)
 		close(cmd->in);
 
+	if (need_out)
+		close(fdout[1]);
+	else if (cmd->out > 1)
+		close(cmd->out);
+
 	return 0;
 }
 
@@ -62,6 +88,8 @@
 {
 	if (cmd->close_in)
 		close(cmd->in);
+	if (cmd->close_out)
+		close(cmd->out);
 
 	for (;;) {
 		int status, code;
diff --git a/run-command.h b/run-command.h
index ff09067..1c9126b 100644
--- a/run-command.h
+++ b/run-command.h
@@ -15,7 +15,9 @@
 	const char **argv;
 	pid_t pid;
 	int in;
+	int out;
 	unsigned close_in:1;
+	unsigned close_out:1;
 	unsigned no_stdin:1;
 	unsigned git_cmd:1; /* if this is to be git sub-command */
 	unsigned stdout_to_stderr:1;