Initial vim syntax for just

including:
- operators
- quotes/strings
- raw quotes/strings
- backtick sub-shells
- curly substitutions
- "set shell" handling

vim-just/example/justfile

@@ -0,0 +1,55 @@
+#!/usr/bin/env oh-no
+# vim:filetype=just
+
+set shell := ["python", "-c"]
+set something
+
+alias d := dogs
+
+export HOTDOGPARTY := hats
+
+now_ish := `print("oh gee")` + `print(sum([1, 2, 5]))`
+
+an_string := "sit ready \"for reals\" 'uh huh' {{an_raw_string + '{{what' }}"
+
+an_raw_string := 'sit ready "wow" {{not_gonna}}'
+
+hats := '''
+very serious hat's
+'''
+
+wats := """
+    {{an_string}} \"yay\" 'ok'
+
+  {{ 'dog' + just_executable()}}
+
+  {{justfile()}}
+
+  {{justfile_directory()}}
+
+{{arch()}} {{os()}}
+  """
+
+serious_business := ```
+from __future__ import print_function
+import os
+import datetime
+
+print(f"home: {os.environ.get("HOME", "?")}")
+print(f"now-ish: {datetime.datetime.now()}")
+```
+
+dogs: aminal manimal _secret
+
+# show the aminal by kind
+aminal kind='dog':
+  #!/usr/bin/env python
+  import sys
+  import os
+  print('\n'.join(os.environ.keys()), file=sys.stderr)
+
+_secret +WHATEVER='OK':
+  @echo "don't tell anyone {{WHATEVER}}"
+
+manimal:
+  @echo wow

vim-just/ftdetect/just.vim

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+autocmd BufReadPost justfile,*.justfile setfiletype just

vim-just/syntax/just.vim

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+" Vim syntax file
+" Language: Just Command Runner
+" Maintainer: Dan Buch
+" Latest Revision: 22 May 2021
+
+if exists("b:current_syntax")
+  finish
+endif
+
+let b:shell_name = "sh"
+let b:load_time_cursor = getpos('.')
+let b:debug = $JUST_VIM_DEBUG == 'enabled'
+
+function JustGetShellName()
+  let lineno = 0
+
+  while lineno < line("$")
+    let lineno += 1
+    let line = getline(lineno)
+
+    let set_shell_match = "^ *set  *shell  *:"
+    if matchstr(line, set_shell_match) == ""
+      if b:debug
+        echom "line number " . lineno . " does not match '" . set_shell_match . "': '" . line . "'"
+      endif
+
+      continue
+    endif
+
+    if b:debug
+      echom "found matching line number " . lineno . ": " . line
+    endif
+
+    :normal /"<CR>lv/"<CR>hy:nohl
+    let shell_name = @"
+
+    if shell_name != ""
+      return shell_name
+    fi
+  endwhile 
+
+  return "sh"
+endfunc
+
+try
+  let shell_name = JustGetShellName()
+
+  if b:debug
+    echom "found shell name: '" . shell_name . "'"
+  endif
+
+  exe "syn include @setshellsyntax syntax/" . shell_name . ".vim"
+
+  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
+endtry
+
+syn keyword justKeyword alias export if else set
+
+syn keyword justFunction arch os os_family
+syn keyword justFunction env_var env_var_or_default invocation_directory
+syn keyword justFunction justfile justfile_directory just_executable
+
+syn keyword justSetting shell export dotenv-load positional-arguments
+
+syn match justOperator /\v:/
+syn match justOperator /\v\)/
+syn match justOperator /\v\(/
+syn match justOperator /\v\=/
+syn match justOperator /\v:\=/
+
+syn match justQuote /\v"/
+syn match justQuote /\v'/
+syn match justQuote /\v"""/
+syn match justQuote /\v'''/
+
+syn match justBacktick /\v\`/
+syn match justBacktick /\v\`\`\`/
+
+syn match justCurlyBrace /\v\{\{/
+syn match justCurlyBrace /\v\}\}/
+
+syn region justCurlyBraced matchgroup=justCurlyBrace start=/\v\{\{/ skip=/\v\\\{/ end=/\v\}\}/ contains=justKeyword,justFunction,justOperator,justQuote,justString,justRawString
+
+syn region justString matchgroup=justQuote start=/\v"/ skip=/\v\\"/ end=/\v"/ contains=justCurlyBraced
+syn region justString matchgroup=justQuote start=/\v"""/ skip=/\v\\"/ end=/\v"""/ contains=justCurlyBraced
+
+syn region justRawString matchgroup=justQuote start=/\v'/ end=/\v'/
+syn region justRawString matchgroup=justQuote start=/\v'''/ end=/\v'''/
+
+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
+
+syn match justComment /\v#.*$/
+
+syn match justShebang /\v^ *#!.*$/
+
+hi def link justKeyword Keyword
+hi def link justSetting Keyword
+hi def link justOperator Operator
+hi def link justComment Comment
+hi def link justShebang PreProc
+hi def link justFunction Function
+hi def link justQuote String
+hi def link justString String
+hi def link justRawString String
+hi def link justCurlyBrace Keyword
+hi def link justBacktick Special
+
+let b:current_syntax = "just"
+
+" vim:expandtab:ts=2:sts=2