Windows: Implement start_command().

On Windows, we have spawnv() variants to run a child process instead of
fork()/exec(). In order to attach pipe ends to stdin, stdout, and stderr,
we have to use this idiom:

    save1 = dup(1);
    dup2(pipe[1], 1);
    spawnv();
    dup2(save1, 1);
    close(pipe[1]);

assuming that the descriptors created by pipe() are not inheritable.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>

1 files changed, 83 insertions, 14 deletions

diff --git a/run-command.c b/run-command.c
index 44100a749b..dd8b7751ce 100644
--- a/run-command.c
+++ b/run-command.c
@@ -65,21 +65,8 @@ int start_command(struct child_process *cmd)
 		cmd->err = fderr[0];
 	}
 
+#ifndef __MINGW32__
 	cmd->pid = fork();
-	if (cmd->pid < 0) {
-		if (need_in)
-			close_pair(fdin);
-		else if (cmd->in)
-			close(cmd->in);
-		if (need_out)
-			close_pair(fdout);
-		else if (cmd->out)
-			close(cmd->out);
-		if (need_err)
-			close_pair(fderr);
-		return -ERR_RUN_COMMAND_FORK;
-	}
-
 	if (!cmd->pid) {
 		if (cmd->no_stdin)
 			dup_devnull(0);
@@ -128,6 +115,88 @@ int start_command(struct child_process *cmd)
 		}
 		die("exec %s failed.", cmd->argv[0]);
 	}
+#else
+	int s0 = -1, s1 = -1, s2 = -1;	/* backups of stdin, stdout, stderr */
+	const char *sargv0 = cmd->argv[0];
+	char **env = environ;
+	struct strbuf git_cmd;
+
+	if (cmd->no_stdin) {
+		s0 = dup(0);
+		dup_devnull(0);
+	} else if (need_in) {
+		s0 = dup(0);
+		dup2(fdin[0], 0);
+	} else if (cmd->in) {
+		s0 = dup(0);
+		dup2(cmd->in, 0);
+	}
+
+	if (cmd->no_stderr) {
+		s2 = dup(2);
+		dup_devnull(2);
+	} else if (need_err) {
+		s2 = dup(2);
+		dup2(fderr[1], 2);
+	}
+
+	if (cmd->no_stdout) {
+		s1 = dup(1);
+		dup_devnull(1);
+	} else if (cmd->stdout_to_stderr) {
+		s1 = dup(1);
+		dup2(2, 1);
+	} else if (need_out) {
+		s1 = dup(1);
+		dup2(fdout[1], 1);
+	} else if (cmd->out > 1) {
+		s1 = dup(1);
+		dup2(cmd->out, 1);
+	}
+
+	if (cmd->dir)
+		die("chdir in start_command() not implemented");
+	if (cmd->env) {
+		env = copy_environ();
+		for (; *cmd->env; cmd->env++)
+			env = env_setenv(env, *cmd->env);
+	}
+
+	if (cmd->git_cmd) {
+		strbuf_init(&git_cmd, 0);
+		strbuf_addf(&git_cmd, "git-%s", cmd->argv[0]);
+		cmd->argv[0] = git_cmd.buf;
+	}
+
+	cmd->pid = spawnvpe(_P_NOWAIT, cmd->argv[0], cmd->argv, (const char **)env);
+
+	if (cmd->env)
+		free_environ(env);
+	if (cmd->git_cmd)
+		strbuf_release(&git_cmd);
+
+	cmd->argv[0] = sargv0;
+	if (s0 >= 0)
+		dup2(s0, 0), close(s0);
+	if (s1 >= 0)
+		dup2(s1, 1), close(s1);
+	if (s2 >= 0)
+		dup2(s2, 2), close(s2);
+#endif
+
+	if (cmd->pid < 0) {
+		if (need_in)
+			close_pair(fdin);
+		else if (cmd->in)
+			close(cmd->in);
+		if (need_out)
+			close_pair(fdout);
+		else if (cmd->out)
+			close(cmd->out);
+		if (need_err)
+			close_pair(fderr);
+		return -ERR_RUN_COMMAND_FORK;
+	}
 
 	if (need_in)
 		close(fdin[0]);