[PATCH v7 11/17] run-command: allow stdin for run_processes_parallel

While it makes sense not to inherit stdin from the parent process to
avoid deadlocking, it's not necessary to completely ban stdin to
children. An informed user should be able to configure stdin safely. By
setting `some_child.process.no_stdin=1` before calling `get_next_task()`
we provide a reasonable default behavior but enable users to set up
stdin streaming for themselves during the callback.

`some_child.process.stdout_to_stderr`, however, remains unmodifiable by
`get_next_task()` - the rest of the run_processes_parallel() API depends
on child output in stderr.

Signed-off-by: Emily Shaffer <redacted>
---
 run-command.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/run-command.c b/run-command.c
index ea4d0fb4b1..80c8c97bc1 100644
--- a/run-command.c
+++ b/run-command.c

@@ -1683,6 +1683,9 @@ static int pp_start_one(struct parallel_processes *pp)
 	if (i == pp->max_processes)
 		BUG("bookkeeping is hard");
 
+	/* disallow by default, but allow users to set up stdin if they wish */
+	pp->children[i].process.no_stdin = 1;
+
 	code = pp->get_next_task(&pp->children[i].process,
 				 &pp->children[i].err,
 				 pp->data,

@@ -1694,7 +1697,6 @@ static int pp_start_one(struct parallel_processes *pp)
 	}
 	pp->children[i].process.err = -1;
 	pp->children[i].process.stdout_to_stderr = 1;
-	pp->children[i].process.no_stdin = 1;
 
 	if (start_command(&pp->children[i].process)) {
 		code = pp->start_failure(&pp->children[i].err,

-- 
2.28.0.rc0.142.g3c755180ce-goog