run-command: support custom fd-set in async

This patch adds the possibility to supply a set of non-0 file
descriptors for async process communication instead of the
default-created pipe.

Additionally, we now support bi-directional communiction with the
async procedure, by giving the async function both read and write
file descriptors.

To retain compatiblity and similar "API feel" with start_command,
we require start_async callers to set .out = -1 to get a readable
file descriptor.  If either of .in or .out is 0, we supply no file
descriptor to the async process.

[sp: Note: Erik started this patch, and a huge bulk of it is
     his work.  All bugs were introduced later by Shawn.]

Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/remote-curl.c b/remote-curl.c
index 3edbf5717c..6bb3366264 100644
--- a/remote-curl.c
+++ b/remote-curl.c
@@ -184,13 +184,13 @@ static struct discovery* discover_refs(const char *service)
 	return last;
 }
 
-static int write_discovery(int fd, void *data)
+static int write_discovery(int in, int out, void *data)
 {
 	struct discovery *heads = data;
 	int err = 0;
-	if (write_in_full(fd, heads->buf, heads->len) != heads->len)
+	if (write_in_full(out, heads->buf, heads->len) != heads->len)
 		err = 1;
-	close(fd);
+	close(out);
 	return err;
 }
 
@@ -202,6 +202,7 @@ static struct ref *parse_git_refs(struct discovery *heads)
 	memset(&async, 0, sizeof(async));
 	async.proc = write_discovery;
 	async.data = heads;
+	async.out = -1;
 
 	if (start_async(&async))
 		die("cannot start thread to parse advertised refs");