Set filetype inside file, no file extension, without using shebang

[edrozenberg]

For certain files without extensions or specific syntaxes, it would be great to be able to explicitly set a filetype using a comment at the top of the file. A shebang wouldn't make sense for certain files which are not scripts but are for ex. config files or other miscellaneous or supporting files without extensions.

Example:
Ghostty (text editor) config file named config (no extension, no syntax).

Toward the top of this config file I added the following vim hint which sets the filetype explicitly just for this file, which vim reads and interprets:

#╔═══════════════════════╗
#║ Ghostty configuration ║
#╚═══════════════════════╝

# vim: set filetype=dosini :

#┌───────────────────────┐
#│ General settings      │
#└───────────────────────┘
#theme =
...
...

For vim, this doesn't need to be the first line, but it also can't be further down inside the file. I assume it cannot be below any un-commented lines...?

There was a previous discussion on this which was closed with a workaround resolution that doesn't directly address the need 100%, especially for files which are not scripts and therefore cannot use shebang lines.
#7555

[the-mikedavis]

Duplicate of #729, this feature in Vi is called the mode line