Begin support for watching dgamelaunch games.

watcher.c is a subprocess which uses inotify to watch the inprogress
directories.  A C program is used because node's fs.watch() can't tell
the difference between creation and deletion.

watcher.c

@@ -0,0 +1,101 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/inotify.h>
+#include <sys/select.h>
+#include <unistd.h>
+#include <limits.h>
+#include <dirent.h>
+
+struct watchdir {
+  int wd;
+  char *name;
+};
+
+char ibuf[sizeof(struct inotify_event) + NAME_MAX + 1];
+
+int startwatch(int ifd, char *dir, struct watchdir *w) {
+  DIR *dstream;
+  struct dirent *ent;
+
+  w->name = dir;
+  w->wd = inotify_add_watch(ifd, dir, IN_CREATE|IN_DELETE|IN_DELETE_SELF);
+  if (w->wd < 0) {
+    fprintf(stderr, "Could not watch %s\n", dir);
+    return 1;
+  }
+  dstream = opendir(dir);
+  if (dstream == NULL) {
+    fprintf(stderr, "%s is not a readable directory\n", dir);
+    inotify_rm_watch(ifd, w->wd);
+    w->wd = -1;
+    return 1;
+  }
+  ent = readdir(dstream);
+  while (ent != NULL) {
+    if (strcmp(ent->d_name, ".") && strcmp(ent->d_name, ".."))
+      printf("E %s/%s\n", dir, ent->d_name);
+    ent = readdir(dstream);
+  }
+  closedir(dstream);
+  fflush(stdout);
+  return 0;
+}
+
+int main(int argc, char *argv[]) {
+  int ifd, rsize, off, done, nwatchers, i;
+  char typecode;
+  struct inotify_event *iev;
+  fd_set rfds;
+  struct watchdir *watchers;
+
+  done = 0;
+  nwatchers = argc - 1;
+  iev = (struct inotify_event *) ibuf;
+  ifd = inotify_init();
+  if (nwatchers == 0) {
+    watchers = malloc(sizeof(struct watchdir));
+    nwatchers = 1;
+    startwatch(ifd, ".", watchers);
+  }
+  else {
+    watchers = malloc(nwatchers * sizeof(struct watchdir));
+    for (i = 0; i < nwatchers; i++) {
+      startwatch(ifd, argv[i+1], watchers + i);
+    }
+  }
+
+  while (!done) {
+    FD_ZERO(&rfds);
+    FD_SET(0, &rfds);
+    FD_SET(ifd, &rfds);
+    select(ifd + 1, &rfds, NULL, NULL, NULL);
+    if (FD_ISSET(ifd, &rfds)) {
+      off = 0;
+      rsize = read(ifd, ibuf, sizeof(struct inotify_event) + NAME_MAX + 1);
+      while (off < rsize) {
+        iev = (struct inotify_event *) (ibuf + off);
+        if (iev->mask & IN_CREATE)
+          typecode = 'C';
+        else if (iev->mask & IN_DELETE)
+          typecode = 'D';
+        else
+          typecode = '?';
+        for (i = 0; i < nwatchers; i++) {
+          if (watchers[i].wd == iev->wd)
+            printf("%c %s/%s\n", typecode, watchers[i].name, iev->name);
+        }
+        off += sizeof(struct inotify_event) + iev->len;
+      }
+      fflush(stdout);
+    }
+    if (FD_ISSET(0, &rfds)) {
+      read(0, &typecode, 1);
+      if (typecode == '\n')
+        done = 1;
+    }
+    
+  }
+  close(ifd);
+  return 0;
+}