Documentation for configurable file extension feature

README.markdown

@@ -356,6 +356,19 @@ By default, ST provides a number of snippets for LaTeX editing; the LaTeXTools p
 In addition, the LaTeXTools plugin provides useful completions for both regular and math text; check out files `LaTeX.sublime-completions` and `LaTeX math.sublime-completions` in the LaTeXTools directory for details. Some of these are semi-intelligent: i.e. `bf` expands to `\textbf{}` if you are typing text, and to `\mathbf{}` if you are in math mode. Others allow you to cycle among different completions: e.g. `f` in math mode expands to `\phi` first, but if you hit Tab again you get `\varphi`; if you hit Tab a third time, you get back `\phi`.
 
 
+Support for non-`.tex` files
+----------------------------
+
+LaTeXTools has some degree of support for LaTeX documents that are in files with an extension other than `.tex`. In particular, this feature is designed to work  well with alternative extensions, such as `.ltx`. Other extensions such as `.Rnw` and `.tikz` are supported, but, for now they will be treated as standard LaTeX documents (patches are always welcome!).
+
+This behaviour is controlled through two settings, `tex_file_exts` and `latextools_set_syntax`.
+
+* `tex_file_exts` (`['.tex']`): a list of extensions that should be considered TeX documents. Any extensions in this list will be treated exactly the same as `.tex` files: they can serve as the TeX master file, they will be searched (if included) for labels or bibliographies, etc.
+* `latextools_set_syntax` (`true`): if `true` LaTeXTools will automatically set the syntax to `LaTeX` when opening or saving any file with an extension in the `tex_file_exts` list.
+
+Note that while the extension detection is used by features of LaTeXTools, including, other features---especially the auto-completions---depend on the syntax of the file being set to `LaTeX` as well.
+
+
 Miscellaneous
 -------------
 
@@ -388,6 +401,8 @@ The following options are currently available (defaults in parentheses):
 - `forward_sync` (`true`): if `true`, after compiling a tex file, the PDF viewer is asked to sync to the position corresponding to the current cursor location in ST. You can also *temporarily* toggle this behavior with `C-l,t,s`.
 - `temp_files_exts`: list of file extensions to be considered temporary, and hence deleted using the `C-l, backspace` command.
 - `temp_files_ignored_folders`: subdirectories to skip when deleting temp files.
+* `tex_file_exts` (`['.tex']`): a list of extensions that should be considered TeX documents. Any extensions in this list will be treated exactly the same as `.tex` files. See the section on [Support for non-`.tex` files](#support-for-non-tex-files).
+* `latextools_set_syntax` (`true`): if `true` LaTeXTools will automatically set the syntax to `LaTeX` when opening or saving any file with an extension in the `tex_file_exts` list.
 
 **Platform settings**:
 - all platforms: