run_command_opt(): optionally hide stderr when the command succeeds

This will be needed to hide the output of `git commit` when the
sequencer handles an interactive rebase's script.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

run-command.c

@@ -576,6 +576,29 @@ int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const
 	cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 	cmd.dir = dir;
 	cmd.env = env;
+
+	if (opt & RUN_HIDE_STDERR_ON_SUCCESS) {
+		struct strbuf buf = STRBUF_INIT;
+		int res;
+
+		cmd.err = -1;
+		if (start_command(&cmd) < 0)
+			return -1;
+
+		if (strbuf_read(&buf, cmd.err, 0) < 0) {
+			close(cmd.err);
+			finish_command(&cmd); /* throw away exit code */
+			return -1;
+		}
+
+		close(cmd.err);
+		res = finish_command(&cmd);
+		if (res)
+			fputs(buf.buf, stderr);
+		strbuf_release(&buf);
+		return res;
+	}
+
 	return run_command(&cmd);
 }
 

run-command.h

@@ -70,6 +70,7 @@ extern int run_hook_ve(const char *const *env, const char *name, va_list args);
 #define RUN_SILENT_EXEC_FAILURE 8
 #define RUN_USING_SHELL 16
 #define RUN_CLEAN_ON_EXIT 32
+#define RUN_HIDE_STDERR_ON_SUCCESS 64
 int run_command_v_opt(const char **argv, int opt);
 
 /*