How to force Vim to open given file as another filetype? (e.g. .txt.gz?)

Question

Problem: I have .glabels generated files, which are gzipped xml. When I rename file to have suffix .xml.gz, then VIM properly recognizes file and it's editable, human readable xml. After edit I have to rename back to original name.

What I try to open e.g. x.glabels file without renaming, what happens is that I see binary data. It does not ungzipped it.

How to force Vim from command like to treat given file like .gz ?

If possible please make answer more general, to address general problem : how to make Vim , treat file .extension1 as file .another_extension ?

Use case: http://glabels.org/ uses gzipped xml, so instead of .glabels extension, they could use .xml.gz.

When I rename file by adding .txt.gz or .xml.gz extension, VIM properly picks it up. However with .glabels extension it treats files like binary.

Question : How to force VIM from commandline to open given file (e.g. "x.glabels") like another type (e.g. "x.xml.gz") ?

No Answers: I know I can make symlink or temporarily rename file. I wonder about VIM flags.

Bonus Addition to answer: You are welcome to include in your answer nice way of configuring VIM to treat e.g. .glabels as .xml.gz, but this won't be accepted as full answer, as I look for onliner that I can use on any machine I will have to deal with. Still, information about config might be helpful for other readers (or my main machines;) ).

Answer 1

There are two answers to your question:

General

In order to open a file, overriding the default filetype detection, you can just specify a :setf[iletype] command as part of :edit. For example:

:edit +setf\ java strange.cpp

The default filetype detection does not change an existing filetype, that's how this works. Of course, you can also do this retroactively via :setl filetype=...

Extending the gzip plugin

As a binary format, Vim cannot directly edit [GZIP] archives. The built-in :help gzip plugin hooks into the filetype detection in order to transparently handle archives. This is done via :autocmds. If you want to support other file extensions, the default ones (cp. :autocmd gzip) need to be extended with the following:

autocmd! BufReadPre *.glabels setlocal binary
autocmd! BufRead *.glabels call gzip#read("gzip -S.glabels -dn")

Note the -S.glabels addition; without this, gzip wouldn't know what to do with the file.