My to-do list is a plain text .txt file that I load in Vim. In .txt files Vim has always coloured hash marks (#) and the text following them on the same line, which I use to mark out urgent to-do items. The other day this highlighting disappeared and I can't for the life of me see how to restore it. I've turned on all the syntax and filetype commands I can find. Should I have a text.vim or txt.vim syntax file that I might've deleted without realising? It feels like there should be a simple solution, but I can't find anything approaching a simple solution from googling round - I'm certainly not going to reinstall, write a custom syntax file, use a complex script, etc., I just want the default behaviour back.
I don't think that your Vim is broken. Try putting a hash mark (#) at the beginning of the first line in the file. When Vim sees this, it sets the filetype to conf (for a configuration file). As far as I know, Vim does not syntax color vanilla text files.
Vim supports modelines. To force coloring the file as
conf (erichui's answer), put the following line at the end or beginning of your file:
# vim: syntax=conf
This sets vim's internal variable
Note: you could also set
ft) instead of