set commentstring in ftplugin

[dhduvall]

Vim documents commentstring as

Currently only used to add markers for folding

which might explain why many filetype plugins don't set it; but I discovered that vim-commentary uses it, so I think it's helpful to have set usefully. I was surprised to find it prepending # to the commented-out lines, but that was probably because of some other plugin setting it globally instead of locally.

Easy workaround:

autocmd FileType cs setl commentstring=//%s

[nickspoons]

I'm not really sure if it's appropriate to set this, just for the sake of vim-commentary. Especially since the global vim default of /*%s*/ is valid in C#.

[dhduvall]

Fair enough. I didn't look for other users; I just hypothesized their existence. I'll defer to you on this. (I should definitely track down what plugin set it globally, though—that seems like a bug.)

[nickspoons]

You can find out where an option was set using :verbose, e.g.:

:verb set commentstring?

[nickspoons]

The commentstring is now included, see #71. Both vim and neovim now include built-in commenting functionality which make use of it, and it has become much more standard to set the option in filetype plugins.