Make the shell detection better?

vim-just/syntax/just.vim

@@ -11,7 +11,7 @@ let b:shell_name = "sh"
 let b:load_time_cursor = getpos('.')
 let b:debug = $JUST_VIM_DEBUG == 'enabled'
 
-function JustGetShellName()
+function! s:justGetShellName()
   let lineno = 0
 
   while lineno < line("$")
@@ -31,35 +31,47 @@ function JustGetShellName()
       echom "found matching line number " . lineno . ": " . line
     endif
 
-    :normal /"<CR>lv/"<CR>hy:nohl
-    let shell_name = @"
+    :normal /"<CR>lv/"<CR>h"ay:nohl
+    let shell_name = @a
 
     if shell_name != ""
+      if b:debug
+        echom "returning shell_name: '" . shell_name . "'"
+      endif
+
       return shell_name
-    fi
-  endwhile 
+    endif
+  endwhile
 
   return "sh"
 endfunc
 
-try
-  let shell_name = JustGetShellName()
+function! s:justSetShellName(shell_name)
+  try
+    if b:debug
+      echom "using shell name: '" . a:shell_name . "'"
+    endif
 
-  if b:debug
-    echom "found shell name: '" . shell_name . "'"
-  endif
+    exe "syn include @setshellsyntax syntax/" . a:shell_name . ".vim"
 
-  exe "syn include @setshellsyntax syntax/" . shell_name . ".vim"
+    let b:shell_name = a:shell_name
+  catch
+    if b:debug
+      echom "oh no: " v:exception
+      echom "falling back to sh syntax"
+    endif
 
-  let b:shell_name = shell_name
-catch
-  if b:debug
-    echom "oh no: " v:exception
-    echom "just.vim: falling back to sh syntax"
-  endif
+    syn include @setshellsyntax syntax/sh.vim
+  finally
+    syn region justSubshell matchgroup=justBacktick start=/\v\`/ skip=/\v\\\`/ end=/\v\`/ contains=@setshellsyntax
+    syn region justSubshell matchgroup=justBacktick start=/\v\`\`\`/ skip=/\v\\\`/ end=/\v\`\`\`/ contains=@setshellsyntax
+  endtry
+endfunc
 
-  syn include @setshellsyntax syntax/sh.vim
-endtry
+call s:justSetShellName(s:justGetShellName())
+
+delfunc s:justSetShellName
+delfunc s:justGetShellName
 
 syn keyword justKeyword alias export if else set