examples: run fetch in a background thread

This allows us to give updates on how it's doing

examples/network/fetch.c

@@ -3,33 +3,76 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <pthread.h>
+
+struct dl_data {
+	git_remote *remote;
+	git_off_t *bytes;
+	git_indexer_stats *stats;
+	int ret;
+	int finished;
+};
+
+static void *download(void *ptr)
+{
+	struct dl_data *data = (struct dl_data *)ptr;
+
+	// Connect to the remote end specifying that we want to fetch
+	// information from it.
+	if (git_remote_connect(data->remote, GIT_DIR_FETCH) < 0) {
+		data->ret = -1;
+		goto exit;
+	}
+
+	// Download the packfile and index it. This function updates the
+	// amount of received data and the indexer stats which lets you
+	// inform the user about progress.
+	if (git_remote_download(data->remote, data->bytes, data->stats) < 0) {
+		data->ret = -1;
+		goto exit;
+	}
+
+	data->ret = 0;
+
+exit:
+	data->finished = 1;
+	pthread_exit(&data->ret);
+}
 
 int fetch(git_repository *repo, int argc, char **argv)
 {
   git_remote *remote = NULL;
   git_off_t bytes = 0;
   git_indexer_stats stats;
-  char *packname = NULL;
+  pthread_t worker;
+  struct dl_data data;
 
-  // Get the remote and connect to it
+  // Figure out whether it's a named remote or a URL
   printf("Fetching %s\n", argv[1]);
-  if (git_remote_load(&remote, repo, argv[1]) == GIT_ENOTFOUND) {
+  if (git_remote_load(&remote, repo, argv[1]) < 0) {
 	  if (git_remote_new(&remote, repo, argv[1], NULL) < 0)
 		  return -1;
   }
 
-  if (git_remote_connect(remote, GIT_DIR_FETCH) < 0)
-	  return -1;
+  // Set up the information for the background worker thread
+  data.remote = remote;
+  data.bytes = &bytes;
+  data.stats = &stats;
+  data.ret = 0;
+  data.finished = 0;
+  memset(&stats, 0, sizeof(stats));
 
-  // Download the packfile and index it
-  // Doing this in a background thread and printing out what bytes
-  // and stats.{processed,total} say would make the UI friendlier
-  if (git_remote_download(remote, &bytes, &stats) < 0) {
-	  git_remote_free(remote);
-	  return -1;
-  }
+  pthread_create(&worker, NULL, download, &data);
 
-  printf("Received %d objects in %d bytes\n", stats.total, bytes);
+  // Loop while the worker thread is still running. Here we show processed
+  // and total objects in the pack and the amount of received
+  // data. Most frontends will probably want to show a percentage and
+  // the download rate.
+  do {
+	usleep(10000);
+	printf("\rReceived %d/%d objects in %d bytes", stats.processed, stats.total, bytes);
+  } while (!data.finished);
+  printf("\rReceived %d/%d objects in %d bytes\n", stats.processed, stats.total, bytes);
 
   // Update the references in the remote's namespace to point to the
   // right commits. This may be needed even if there was no packfile