The easiest way to find all the options that affect indenting is to open an options window with
:options
and then look at Section 15, "tabs and indenting". Once you know which options are relevant, you can check their current values and which plugin is responsible with
:verbose set ai? si? cin? cink? inde? indk? ci? pi? lisp? lispw?
To actually disable a filetype-specific indentation; from the manual section 30.3:
If you don't like the indenting for one specific type of file, this is how you avoid it. Create a file with just this one line: >
:let b:did_indent = 1
Now you need to write this in a file with a specific name:
/indent/.vim
The is the name of the file type, such as "cpp" or "java".