GFileMonitor: add APPEARED event

...and try to send it for some common cases in inotify.

We're now abusing the WATCH_MOVES flag as a general "opt-in to new API".
That's bad.

gio/gio.c

@@ -67,6 +67,10 @@ gio_watch_callback (GFileMonitor      *monitor,
       g_assert (!other);
       g_print ("%s: deleted", child_str);
       break;
+    case G_FILE_MONITOR_EVENT_APPEARED:
+      g_assert (!other);
+      g_print ("%s: appeared", child_str);
+      break;
     case G_FILE_MONITOR_EVENT_CREATED:
       g_assert (!other);
       g_print ("%s: created", child_str);

gio/gioenums.h

@@ -422,6 +422,7 @@ typedef enum {
   G_FILE_MONITOR_EVENT_PRE_UNMOUNT,
   G_FILE_MONITOR_EVENT_UNMOUNTED,
   G_FILE_MONITOR_EVENT_MOVED,
+  G_FILE_MONITOR_EVENT_APPEARED,
   G_FILE_MONITOR_EVENT_RENAMED,
   G_FILE_MONITOR_EVENT_MOVED_IN,
   G_FILE_MONITOR_EVENT_MOVED_OUT

gio/glocalfilemonitor.c

@@ -387,6 +387,14 @@ g_file_monitor_source_handle_event (GFileMonitorSource *fms,
         }
       break;
 
+    case G_FILE_MONITOR_EVENT_APPEARED:
+      g_assert (!other && !rename_to);
+      if (fms->flags & G_FILE_MONITOR_WATCH_MOVES)
+        g_file_monitor_source_send_event (fms, event_type, child, NULL);
+      else
+        g_file_monitor_source_send_synthetic_created (fms, child);
+      break;
+
     case G_FILE_MONITOR_EVENT_DELETED:
     case G_FILE_MONITOR_EVENT_ATTRIBUTE_CHANGED:
     case G_FILE_MONITOR_EVENT_PRE_UNMOUNT:

gio/inotify/inotify-helper.c

@@ -27,6 +27,7 @@
 #include <time.h>
 #include <string.h>
 #include <sys/ioctl.h>
+#include <sys/stat.h>
 /* Just include the local header to stop all the pain */
 #include <sys/inotify.h>
 #include <gio/glocalfilemonitor.h>
@@ -193,8 +194,42 @@ ih_event_callback (ik_event_t  *event,
             g_object_unref (other);
         }
     }
+  else if (event->mask & IN_CREATE)
+    {
+      GFileMonitorEvent event_type;
+      const gchar *parent_dir;
+      gchar *fullname;
+      struct stat buf;
+      gint s;
+
+      /* The kernel reports IN_CREATE for two types of events:
+       *
+       *  - creat(), in which case IN_CLOSE_WRITE will come soon; or
+       *  - link(), mkdir(), mknod(), etc., in which case it won't
+       *
+       * We can attempt to detect the second case and turn it into an
+       * APPEARED event so that the user isn't expecting CHANGES_DONE.
+       *
+       * The detection for link() is not 100% reliable since the link
+       * count could be 1 if the original link was deleted or if
+       * O_TMPFILE was being used, but in that case the virtual
+       * CHANGES_DONE will be emitted to close the loop.
+       */
+
+      parent_dir = _ip_get_path_for_wd (event->wd);
+      fullname = _ih_fullpath_from_event (event, parent_dir, NULL);
+      s = stat (fullname, &buf);
+      g_free (fullname);
+
+      /* does it look like the result of creat()? */
+      if (s == 0 && S_ISREG (buf.st_mode) && buf.st_nlink == 1)
+        event_type = G_FILE_MONITOR_EVENT_CREATED;
+      else
+        event_type = G_FILE_MONITOR_EVENT_APPEARED;
+
+      g_file_monitor_source_handle_event (sub->user_data, event_type, event->name, NULL, NULL, event->timestamp);
+    }
   else
-    /* unpaired event -- no 'other' field */
     g_file_monitor_source_handle_event (sub->user_data, ih_mask_to_EventFlags (event->mask),
                                         event->name, NULL, NULL, event->timestamp);
 }
@@ -202,7 +237,7 @@ ih_event_callback (ik_event_t  *event,
 static void
 ih_not_missing_callback (inotify_sub *sub)
 {
-  g_file_monitor_source_handle_event (sub->user_data, G_FILE_MONITOR_EVENT_CREATED,
+  g_file_monitor_source_handle_event (sub->user_data, G_FILE_MONITOR_EVENT_APPEARED,
                                       sub->filename, NULL, NULL, g_get_monotonic_time ());
 }