Implement #if, #else, #elseif, #endif directives.

These are shortcuts for one-line verbatim blocks. See the test.

Fixes #14.

autoload/colortemplate.vim

@@ -1,9 +1,10 @@
 " vim: foldmethod=marker nowrap
 let s:VERSION = '2.0.0b1'
-" Grammar {{{
+" Informal grammar {{{
 " <Template>                  ::= <Line>*
 " <Line>                      ::= <EmptyLine> | <Comment> | <KeyValuePair> | <HiGroupDef> |
-"                                 <VerbatimText>  | <AuxFile> | <Documentation>
+"                                 <VerbatimText>  | <Command> | <AuxFile> | <Documentation>
+" <Command>                   ::= #if <Anything> | #elseif <Anything> | #else | #endif
 " <VerbatimText>              ::= verbatim <Anything> endverbatim
 " <AuxFile>                   ::= auxfile <Path> <Anything> endauxfile
 " <Path>                      ::= .+
@@ -1110,7 +1111,11 @@ fun! s:token.next() dict
     let [self.value, self.spos, self.pos] = matchstrpos(s:getl(), '\d\+', self.pos - 1)
     let self.kind = 'NUM'
   elseif l:char ==# '#'
-    if match(s:getl(), '^[0-9a-f]\{6}', self.pos) > -1
+    " Commands are recognized only at the start of a line
+    if match(s:getl(), '^\s*#\%(if\|else\%[if]\|endif\)\>', 0) > -1
+      let self.kind = 'CMD'
+      let self.value = matchstr(s:getl(), '^\s*#\zs\%(if\|else\%[if]\|endif\)\>', 0)
+    elseif match(s:getl(), '^[0-9a-f]\{6}', self.pos) > -1
       let [self.value, self.spos, self.pos] = matchstrpos(s:getl(), '#[0-9a-f]\{6}', self.pos - 1)
       let self.kind = 'HEX'
     else
@@ -1429,6 +1434,8 @@ fun! s:parse_line()
     else
       call s:parse_hi_group_def()
     endif
+  elseif s:token.kind ==# 'CMD'
+    call s:parse_command(s:token.value)
   else
     throw 'Unexpected token at start of line'
   endif
@@ -1755,6 +1762,14 @@ fun! s:parse_linked_group_def()
     call s:add_linked_item(l:v, s:active_section(), l:source_group, s:token.value)
   endfor
 endf
+
+fun! s:parse_command(cmd)
+  let l:text = matchstr(s:getl(), '^\s*#\zs.\{-}\s*$')
+  for l:v in s:active_variants()
+    call s:add_verbatim_item(l:v, s:active_section(),
+          \ { 'line': l:text, 'linenr': s:linenr(), 'file': s:currfile() })
+  endfor
+endf
 " }}} Parser
 " Init/clear parser {{{
 fun! s:init_parser()

syntax/colortemplate.vim

@@ -150,6 +150,7 @@ syn include @colortemplatevim syntax/vim.vim
 unlet b:current_syntax
 syn region colortemplatevim matchgroup=colortemplateKeyword start=/verbatim/ end=/endverbatim/ keepend contains=@colortemplatevim
 syn region auxfilevim       matchgroup=colortemplateKeyword start=/auxfile.*\.vim$/ end=/endauxfile/ keepend contains=@colortemplatevim
+syn region colortemplateCommand matchgroup=colortemplateCommand start=/^\s*#\%(if\|else\%[if]\|endif\)\>/ end=/$/ keepend contains=@colortemplatevim
 
 syn include @colortemplatehelp syntax/help.vim
 unlet b:current_syntax
@@ -158,6 +159,7 @@ syn region colortemplatehelp matchgroup=colortemplateKeyword start=/documentatio
 hi def link colortemplateArrow        Delimiter
 hi def link colortemplateAttr         Label
 hi def link colortemplateAttrs        String
+hi def link colortemplateCommand      PreProc
 hi def link colortemplateConstant     Type
 hi def link colortemplateComment      Comment
 hi def link colortemplateFunction     Function

test/expected/test58.vim

@@ -0,0 +1,28 @@
+" Name:         Test 58
+" Author:       y
+" Maintainer:   y
+" License:      Vim License (see `:help license`)
+
+set background=dark
+
+hi clear
+if exists('syntax_on')
+  syntax reset
+endif
+
+let g:colors_name = 'test58'
+
+let s:t_Co = exists('&t_Co') && !empty(&t_Co) && &t_Co > 1 ? &t_Co : 2
+
+if (has('termguicolors') && &termguicolors) || has('gui_running')
+  if 1 " some condition
+    hi Normal guifg=#ffffff guibg=#000000 guisp=NONE gui=NONE cterm=NONE
+  elseif '#000000' == '#ffffff' " interpolation works here
+    hi Normal guifg=#000000 guibg=#ffffff guisp=NONE gui=NONE cterm=NONE
+  else " A comment
+    hi Normal guifg=#000000 guibg=#000000 guisp=NONE gui=NONE cterm=NONE
+  endif " end some condition (255)
+  unlet s:t_Co
+  finish
+endif
+

test/test58.txt

@@ -0,0 +1,16 @@
+# vim: ft=colortemplate
+Full name:Test 58
+Short name:test58
+Author:y
+Variant:gui
+Background:dark
+Color:black rgb(0,0,0) 16 Black
+Color:white #ffffff 255 White
+#if 1 " some condition
+Normal white black #if here is treated as comment
+#elseif '@guiblack' == '@guiwhite' " interpolation works here
+Normal black white #else ditto
+#else " A comment
+Normal black black #elseif ditto
+#endif " end some condition (@termwhite)
+

test/test_colortemplate.vim

@@ -681,6 +681,14 @@ fun! Test_CT_color_typo()
   bwipe test57.txt
 endf
 
+fun! Test_CT_conditional_commands()
+  edit test58.txt
+  Colortemplate!
+  call assert_equal(0, get(g:, 'colortemplate_exit_status', 1))
+  call s:verify('test58')
+  bwipe test58.txt
+endf
+
 let s:old_warnings  = get(g:, 'colortemplate_warnings',       -1)
 let s:old_creator   = get(g:, 'colortemplate_creator',        -1)
 let s:old_timestamp = get(g:, 'colortemplate_timestamp',      -1)