Add an option to conceal preformatted text blocks

This merges PR #641.

autoload/vimwiki/base.vim

@@ -1022,10 +1022,11 @@ function! vimwiki#base#nested_syntax(filetype, start, end, textSnipHl) abort
     let group='texMathZoneGroup'
   endif
 
+  let concealpre = vimwiki#vars#get_global('conceal_pre') ? ' concealends' : ''
   execute 'syntax region textSnip'.ft.
         \ ' matchgroup='.a:textSnipHl.
         \ ' start="'.a:start.'" end="'.a:end.'"'.
-        \ ' contains=@'.group.' keepend'
+        \ ' contains=@'.group.' keepend'.concealpre
 
   " A workaround to Issue 115: Nested Perl syntax highlighting differs from
   " regular one.

autoload/vimwiki/vars.vim

@@ -145,6 +145,7 @@ function! s:read_global_settings_from_user()
         \ 'auto_chdir': {'type': type(0), 'default': 0, 'min': 0, 'max': 1},
         \ 'autowriteall': {'type': type(0), 'default': 1, 'min': 0, 'max': 1},
         \ 'conceallevel': {'type': type(0), 'default': 2, 'min': 0, 'max': 3},
+        \ 'conceal_pre': {'type': type(0), 'default': 0, 'min': 0, 'max': 1},
         \ 'create_link': {'type': type(0), 'default': 1, 'min':0, 'max': 1},
         \ 'diary_months': {'type': type({}), 'default':
         \   {

doc/vimwiki.txt

@@ -2887,6 +2887,26 @@ URLs and hides markers and URL for links that have a description.
 Default: 2
 
 
+------------------------------------------------------------------------------
+*g:vimwiki_conceal_pre*
+
+Conceal preformatted text markers. For example,
+>
+    {{{python
+    def say_hello():
+        print("Hello, world!")
+    }}}
+>
+would appear as simply
+>
+    def say_hello():
+        print("Hello, world!")
+>
+in your wiki file.
+
+Default: 0
+
+
 ------------------------------------------------------------------------------
 *g:vimwiki_autowriteall*
 

syntax/vimwiki.vim

@@ -318,8 +318,9 @@ execute 'syntax match VimwikiCodeT /'.vimwiki#vars#get_syntaxlocal('rxCode').
 " <hr> horizontal rule
 execute 'syntax match VimwikiHR /'.vimwiki#vars#get_syntaxlocal('rxHR').'/'
 
-execute 'syntax region VimwikiPre start=/'.vimwiki#vars#get_syntaxlocal('rxPreStart').
-      \ '/ end=/'.vimwiki#vars#get_syntaxlocal('rxPreEnd').'/ contains=@Spell'
+let concealpre = vimwiki#vars#get_global('conceal_pre') ? ' concealends' : ''
+execute 'syntax region VimwikiPre matchgroup=VimwikiPreDelim start=/'.vimwiki#vars#get_syntaxlocal('rxPreStart').
+      \ '/ end=/'.vimwiki#vars#get_syntaxlocal('rxPreEnd').'/ contains=@Spell'.concealpre
 
 execute 'syntax region VimwikiMath start=/'.vimwiki#vars#get_syntaxlocal('rxMathStart').
       \ '/ end=/'.vimwiki#vars#get_syntaxlocal('rxMathEnd').'/ contains=@Spell'
@@ -395,6 +396,7 @@ hi def link VimwikiCodeT VimwikiCode
 
 hi def link VimwikiPre PreProc
 hi def link VimwikiPreT VimwikiPre
+hi def link VimwikiPreDelim VimwikiPre
 
 hi def link VimwikiMath Number
 hi def link VimwikiMathT VimwikiMath