run-command: allow capturing of collated output

Some callers, for example server-side hooks which wish to relay hook
output to clients across a transport, want to capture what would
normally print to stderr and do something else with it. Allow that via a
callback.

By calling the callback regardless of whether there's output available,
we allow clients to send e.g. a keepalive if necessary.

Because we expose a strbuf, not a fd or FILE*, there's no need to create
a temporary pipe or similar - we can just skip the print to stderr and
instead hand it to the caller.

Signed-off-by: Emily Shaffer <emilyshaffer@google.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 22 insertions, 8 deletions

diff --git a/run-command.c b/run-command.c
index a608d37fb2..6b1e4a3453 100644
--- a/run-command.c
+++ b/run-command.c
@@ -1595,7 +1595,10 @@ static void pp_cleanup(struct parallel_processes *pp,
 	 * When get_next_task added messages to the buffer in its last
 	 * iteration, the buffered output is non empty.
 	 */
-	strbuf_write(&pp->buffered_output, stderr);
+	if (opts->consume_output)
+		opts->consume_output(&pp->buffered_output, opts->data);
+	else
+		strbuf_write(&pp->buffered_output, stderr);
 	strbuf_release(&pp->buffered_output);
 
 	sigchain_pop_common();
@@ -1734,13 +1737,17 @@ static void pp_buffer_stderr(struct parallel_processes *pp,
 	}
 }
 
-static void pp_output(const struct parallel_processes *pp)
+static void pp_output(const struct parallel_processes *pp,
+		      const struct run_process_parallel_opts *opts)
 {
 	size_t i = pp->output_owner;
 
 	if (child_is_working(&pp->children[i]) &&
 	    pp->children[i].err.len) {
-		strbuf_write(&pp->children[i].err, stderr);
+		if (opts->consume_output)
+			opts->consume_output(&pp->children[i].err, opts->data);
+		else
+			strbuf_write(&pp->children[i].err, stderr);
 		strbuf_reset(&pp->children[i].err);
 	}
 }
@@ -1788,11 +1795,15 @@ static int pp_collect_finished(struct parallel_processes *pp,
 		} else {
 			const size_t n = opts->processes;
 
-			strbuf_write(&pp->children[i].err, stderr);
+			/* Output errors, then all other finished child processes */
+			if (opts->consume_output) {
+				opts->consume_output(&pp->children[i].err, opts->data);
+				opts->consume_output(&pp->buffered_output, opts->data);
+			} else {
+				strbuf_write(&pp->children[i].err, stderr);
+				strbuf_write(&pp->buffered_output, stderr);
+			}
 			strbuf_reset(&pp->children[i].err);
-
-			/* Output all other finished child processes */
-			strbuf_write(&pp->buffered_output, stderr);
 			strbuf_reset(&pp->buffered_output);
 
 			/*
@@ -1829,7 +1840,7 @@ static void pp_handle_child_IO(struct parallel_processes *pp,
 				pp->children[i].state = GIT_CP_WAIT_CLEANUP;
 	} else {
 		pp_buffer_stderr(pp, opts, output_timeout);
-		pp_output(pp);
+		pp_output(pp, opts);
 	}
 }
 
@@ -1852,6 +1863,9 @@ void run_processes_parallel(const struct run_process_parallel_opts *opts)
 					   "max:%"PRIuMAX,
 					   (uintmax_t)opts->processes);
 
+	if (opts->ungroup && opts->consume_output)
+		BUG("ungroup and reading output are mutualy exclusive");
+
 	/*
 	 * Child tasks might receive input via stdin, terminating early (or not), so
 	 * ignore the default SIGPIPE which gets handled by each feed_pipe_fn which