file-coding-system-alist

file-coding-system-alist is a variable defined in `C source code'.
Its value is shown below.

Documentation:
Alist to decide a coding system to use for a file I/O operation.
The format is ((PATTERN . VAL) ...),
where PATTERN is a regular expression matching a file name,
VAL is a coding system, a cons of coding systems, or a function symbol.
If VAL is a coding system, it is used for both decoding and encoding
the file contents.
If VAL is a cons of coding systems, the car part is used for decoding,
and the cdr part is used for encoding.
If VAL is a function symbol, the function must return a coding system
or a cons of coding systems which are used as above. The function is
called with an argument that is a list of the arguments with which
`find-operation-coding-system' was called. If the function can't decide
a coding system, it can return `undecided' so that the normal
code-detection is performed.

See also the function `find-operation-coding-system'
and the variable `auto-coding-alist'.

You can customize this variable.

Value:

(("\\.dz\\'" no-conversion . no-conversion)
 ("\\.txz\\'" no-conversion . no-conversion)
 ("\\.xz\\'" no-conversion . no-conversion)
 ("\\.lzma\\'" no-conversion . no-conversion)
 ("\\.lz\\'" no-conversion . no-conversion)
 ("\\.g?z\\'" no-conversion . no-conversion)
 ("\\.\\(?:tgz\\|svgz\\|sifz\\)\\'" no-conversion . no-conversion)
 ("\\.tbz2?\\'" no-conversion . no-conversion)
 ("\\.bz2\\'" no-conversion . no-conversion)
 ("\\.Z\\'" no-conversion . no-conversion)
 ("\\.elc\\'" . utf-8-emacs)
 ("\\.el\\'" . prefer-utf-8)
 ("\\.utf\\(-8\\)?\\'" . utf-8)
 ("\\.xml\\'" . xml-find-file-coding-system)
 ("\\(\\`\\|/\\)loaddefs.el\\'" raw-text . raw-text-unix)
 ("\\.tar\\'" no-conversion . no-conversion)
 ("\\.po[tx]?\\'\\|\\.po\\." . po-find-file-coding-system)
 ("\\.\\(tex\\|ltx\\|dtx\\|drv\\)\\'" . latexenc-find-file-coding-system)
 ("" undecided))

Original value was

(("\\.elc\\'" . utf-8-emacs)
 ("\\.el\\'" . prefer-utf-8)
 ("\\.utf\\(-8\\)?\\'" . utf-8)
 ("\\.xml\\'" . xml-find-file-coding-system)
 ("\\(\\`\\|/\\)loaddefs.el\\'" raw-text . raw-text-unix)
 ("\\.tar\\'" no-conversion . no-conversion)
 ("\\.po[tx]?\\'\\|\\.po\\." . po-find-file-coding-system)
 ("\\.\\(tex\\|ltx\\|dtx\\|drv\\)\\'" . latexenc-find-file-coding-system)
 ("" undecided))