Add support for Cyrillic in headings

Author: mzlogin

ftplugin/markdown.vim

@@ -114,7 +114,7 @@ function! s:GetHeadingLevel(headingLine)
 endfunction
 
 function! s:GetHeadingLinkGFM(headingName)
-    let l:headingLink = tolower(a:headingName)
+    let l:headingLink = tr(a:headingName, "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz")
 
     " \_^ : start of line
     " _\+ : one of more underscore _
@@ -126,7 +126,7 @@ function! s:GetHeadingLinkGFM(headingName)
     " chinese chars are removed.
     " \\%#=0: allow this pattern to use the regexp engine he wants. Having
     " `set re=1` in the vimrc could break this behavior. cf. issue #19
-    let l:headingLink = substitute(l:headingLink, "\\%#=0[^[:alnum:]\u00C0-\u00FF\u4e00-\u9fbf _-]", "", "g")
+    let l:headingLink = substitute(l:headingLink, "\\%#=0[^[:alnum:]\u00C0-\u00FF\u0400-\u04ff\u4e00-\u9fbf _-]", "", "g")
     let l:headingLink = substitute(l:headingLink, " ", "-", "g")
 
     if l:headingLink ==# ""

test/GFM.md

@@ -13,7 +13,7 @@
     * [1.1 heading with dot 2.1](#11-heading-with-dot-21)
     * [1.1](#11)
         * [heading with some "special" (yes, special) chars: les caractères unicodes](#heading-with-some-special-yes-special-chars-les-caractères-unicodes)
-    * [heading with Cyrillic Б б](#heading-with-cyrillic--)
+    * [heading with Cyrillic Б б](#heading-with-cyrillic-Б-б)
 
 <!-- vim-markdown-toc -->
 

test/test.vim

@@ -65,6 +65,7 @@ call ASSERT(GetHeadingLinkTest("### ![vim-markdown-toc-img](/path/to/a/png)", "G
 call ASSERT(GetHeadingLinkTest("### ![](/path/to/a/png)", "GitLab") ==# "-2")
 call ASSERT(GetHeadingLinkTest("### 1.1", "GitLab") ==# "11")
 call ASSERT(GetHeadingLinkTest("### heading with some \"special\" \(yes, special\) chars: les caractères unicodes", "GitLab") ==# "heading-with-some-special-yes-special-chars-les-caractères-unicodes")
+call ASSERT(GetHeadingLinkTest("## heading with Cyrillic Б б", "GitLab") ==# "heading-with-cyrillic-Б-б")
 
 " Redcarpet Test Cases
 call ASSERT(GetHeadingLinkTest("# -Hello-World-", "Redcarpet") ==# "hello-world")