office: usage text, no session before the project is known good; commands on PATH

bin/office

@@ -236,8 +236,26 @@ def run_on_remote(host, folder, opts):
     return 0
 
 
+USAGE = """office — open a folder as a project
+
+  office <folder> --project "<Name>"        adopt a project Paperclip already has
+  office <folder> --new "<Name>"            create the Paperclip project too
+  office <folder> --project "<Name>" --host nixos-desktop    the folder is on that machine
+  office <folder> --dry                     say what would happen, write nothing
+
+The folder and the session live on the same machine. If you are typing inside the
+session, on the machine that owns the folder, it is just: office <folder>.
+"""
+
+
 def main():
-    opts = parse(sys.argv[1:])
+    argv = sys.argv[1:]
+    if not argv or "-h" in argv or "--help" in argv:
+        h.say(USAGE.strip())
+        return 0
+    opts = parse(argv)
+    if opts["folder"] in ("", "."):
+        raise h.Refused(2, "give the folder: office <folder> --project \"<Name>\"  (office --help)")
     folder = os.path.abspath(os.path.expanduser(opts["folder"]))
     if not os.path.isdir(folder):
         raise h.Refused(2, "no folder at %s" % folder)
@@ -277,9 +295,6 @@ def main():
         h.say("dry run: nothing was written")
         return 0
 
-    if not opts["no_switch"]:
-        ensure_session(session, folder)
-
     if opts["host"] and opts["host"] not in (pj.this_machine(), pj.this_machine().split(".")[0]):
         # Only a note, because the panes are built by the machine that owns them.
         h.say("host: %s (build the pages there)" % host)
@@ -323,6 +338,9 @@ def main():
     pj.save(folder, cfg)
     h.say("wrote   %s" % pj.path(folder))
 
+    if not opts["no_switch"]:
+        ensure_session(session, folder)
+
     pj.register(cfg, proj["name"])
     h.say("recorded in %s" % pj.REGISTRY)