I found the answer to this question while writing it, so I’ve broadened it a little. I wanted to access the --servername argument, in order to create dynamic settings in my .vimrc file.
Through vim’s help, I found the v:servername variable, and my script is working. However, now I’m curious if it’s possible to access any arbitrary command-line argument. For example, if I wanted to know if vim was in Lisp mode (-l) or Debugging mode (-D), how would I do it? There seems to be no corresponding v: variable for them.
Here are the variables I found by autocompleting :help v:<Tab>

Is there a general way to access command-line arguments from vimscript?
Strangely, I think the answer may be “No, there is no direct way to access startup options specified on the command line”.
The
:argscommand andargv()can be used to access the filename(s) specified on startup, but that’s not what you want.I see on Vim’s forums that someone offered this solution to get the startup command line on Linux:
I assume there’s analogous command on Windows. . . .
You can look over that forum thread here:
http://groups.google.com/group/vim_use/browse_thread/thread/43773f27cdc10265/ad17ae8180c0fb6e?show_docid=ad17ae8180c0fb6e