Fixes xuhdev#46

Run tex engine before and after bib executable
Add support for both `bibtex` and `biber`
 - Add global variable `g:latexlivepreview_use_biber`
Add Bibliography section to README
 - Detail usage of `g:latexlivepreview_use_biber`
 - Detail usage with `biblatex`
Clean up calls to bibexec commands
Remove `cd` from processing of bib commands
 - Move code that selects this option to the initializer
Give more meaningful feedback when `engine` and `preview` commands are not valid
 - Throw errors from this context
Catch errors in the initializer and then stop execution
Move README section about bibliographies
Update README to reflect change of g:latexlivepreview_biber
Add section in Known Issues about bibliographies to README
Add auto handling of certain bib setting mismatches
Fix bugged warning when `biblatex` not used
Add latex label to latex code in README
Use snake_case not camelCase

README.md

@@ -129,7 +129,7 @@ Please note that the package `biblatex` can use both `bibtex` and the newer
 `biber`, but uses `biber` by default. To use `bibtex`, add `backend=bibtex`
 to your `biblatex` usepackage declaration.
 
-```
+```latex
 \usepackage[backend=bibtex]{biblatex}
 ```
 
@@ -181,7 +181,7 @@ See [issue #46](https://github.com/xuhdev/vim-latex-live-preview/issues/46) and
 If you're using `biblatex` this is most likely caused by not also setting 
 `g:livepreview_use_biber = 1` in your `.vimrc`. Or if you intended to use
 `bibtex` not using that option when using the `biblatex` package. i.e.
-```
+```latex
 \usepackage[backend=bibtex]{biblatex}
 ```
 

plugin/latexlivepreview.vim

@@ -101,24 +101,24 @@ function! s:StartPreview(...)
     if ( l:position != 0 )
         let l:matches = matchstr(getline(l:position), specific_pattern)
         if ( l:matches == '' )
-            " expect s:useBiber=1
-            if ( s:useBiber == 0 )
-                let s:useBiber = 1
+            " expect s:use_biber=1
+            if ( s:use_biber == 0 )
+                let s:use_biber = 1
                 echohl ErrorMsg
                 echom "g:livepreview_use_biber not set or does not match `biblatex` usage in your document. Overridden!"
                 echohl None
             endif
         else
-            " expect s:useBiber=0
-            if ( s:useBiber == 1 )
-                let s:useBiber = 0
+            " expect s:use_biber=0
+            if ( s:use_biber == 1 )
+                let s:use_biber = 0
                 echohl ErrorMsg
                 echom "g:livepreview_use_biber is set but `biblatex` is explicitly using `bibtex`. Overridden!"
                 echohl None
             endif
         endif
     else
-        " expect s:useBiber=0
+        " expect s:use_biber=0
         " `biblatex` is not being used, this usually means we
         " are using `bibtex`
         " However, it is not a universal rule, so we do nothing.
@@ -217,7 +217,7 @@ EEOOFF
                         \ l:tmp_root_dir . '/' . bib_fn)                                " TODO: may fail if same bibfile names in different dirs
         endfor
 
-        if s:useBiber
+        if s:use_biber
             let s:bibexec = 'biber --input-directory=' . l:tmp_root_dir . '--output-directory=' . l:tmp_root_dir . ' ' . l:root_file
         else
             " The alternative to this pushing and popping is to write
@@ -286,7 +286,7 @@ EEOOFF
     let s:previewer = s:ValidateExecutables('livepreview_previewer', [get(g:, 'livepreview_previewer', ''), 'evince', 'okular'])
 
     " Select bibliography executable
-    let s:useBiber = get(g:, 'livepreview_use_biber', 0)
+    let s:use_biber = get(g:, 'livepreview_use_biber', 0)
 
     return 0
 endfunction