run_processes_parallel: rename parameters for the callbacks

The refs code has a similar pattern of passing around 'struct strbuf *err',
which is strictly used for error reporting. This is not the case here,
as the strbuf is used to accumulate all the output (whether it is error
or not) for the user. Rename it to 'out'.

Suggested-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

run-command.c

@@ -902,15 +902,15 @@ struct parallel_processes {
 	struct strbuf buffered_output; /* of finished children */
 };
 
-static int default_start_failure(struct strbuf *err,
+static int default_start_failure(struct strbuf *out,
 				 void *pp_cb,
 				 void *pp_task_cb)
 {
 	return 0;
 }
 
 static int default_task_finished(int result,
-				 struct strbuf *err,
+				 struct strbuf *out,
 				 void *pp_cb,
 				 void *pp_task_cb)
 {

run-command.h

@@ -139,7 +139,7 @@ int in_async(void);
  * return the negative signal number.
  */
 typedef int (*get_next_task_fn)(struct child_process *cp,
-				struct strbuf *err,
+				struct strbuf *out,
 				void *pp_cb,
 				void **pp_task_cb);
 
@@ -148,7 +148,7 @@ typedef int (*get_next_task_fn)(struct child_process *cp,
  * a new process.
  *
  * You must not write to stdout or stderr in this function. Add your
- * message to the strbuf err instead, which will be printed without
+ * message to the strbuf out instead, which will be printed without
  * messing up the output of the other parallel processes.
  *
  * pp_cb is the callback cookie as passed into run_processes_parallel,
@@ -158,15 +158,15 @@ typedef int (*get_next_task_fn)(struct child_process *cp,
  * To send a signal to other child processes for abortion, return
  * the negative signal number.
  */
-typedef int (*start_failure_fn)(struct strbuf *err,
+typedef int (*start_failure_fn)(struct strbuf *out,
 				void *pp_cb,
 				void *pp_task_cb);
 
 /**
  * This callback is called on every child process that finished processing.
  *
  * You must not write to stdout or stderr in this function. Add your
- * message to the strbuf err instead, which will be printed without
+ * message to the strbuf out instead, which will be printed without
  * messing up the output of the other parallel processes.
  *
  * pp_cb is the callback cookie as passed into run_processes_parallel,
@@ -177,7 +177,7 @@ typedef int (*start_failure_fn)(struct strbuf *err,
  * the negative signal number.
  */
 typedef int (*task_finished_fn)(int result,
-				struct strbuf *err,
+				struct strbuf *out,
 				void *pp_cb,
 				void *pp_task_cb);