Error when core.worktree expected but missing

autoload/fugitive.vim

@@ -88,11 +88,16 @@ function! s:VersionCheck() abort
   endif
 endfunction
 
+let s:worktree_error = "core.worktree is required when using an external Git dir"
 function! s:DirCheck(...) abort
   let vcheck = s:VersionCheck()
   if !empty(vcheck)
     return vcheck
-  elseif !empty(a:0 ? s:Dir(a:1) : s:Dir())
+  endif
+  let dir = a:0 ? s:Dir(a:1) : s:Dir()
+  if !empty(dir) && FugitiveWorkTree(dir, 1) is# 0
+    return 'return ' . string('echoerr "fugitive: ' . s:worktree_error . '"')
+  elseif !empty(dir)
     return ''
   elseif empty(bufname(''))
     return 'return ' . string('echoerr "fugitive: working directory does not belong to a Git repository"')
@@ -2134,8 +2139,10 @@ function! fugitive#BufReadStatus() abort
     if push !=# pull
       call s:AddHeader('Push', push)
     endif
-    if empty(s:Tree())
+    if get(fugitive#ConfigGetAll('core.bare', config), 0, 'true') !~# '^\%(false\|no|off\|0\|\)$'
       call s:AddHeader('Bare', 'yes')
+    elseif empty(s:Tree())
+      call s:AddHeader('Error', s:worktree_error)
     endif
     if get(fugitive#ConfigGetAll('advice.statusHints', config), 0, 'true') !~# '^\%(false\|no|off\|0\|\)$'
       call s:AddHeader('Help', 'g?')
@@ -2867,6 +2874,9 @@ unlet s:colortype
 function! fugitive#Command(line1, line2, range, bang, mods, arg) abort
   exe s:VersionCheck()
   let dir = s:Dir()
+  if len(dir)
+    exe s:DirCheck(dir)
+  endif
   let config = copy(fugitive#Config(dir))
   let [args, after] = s:SplitExpandChain(a:arg, s:Tree(dir))
   let flags = []

plugin/fugitive.vim

@@ -180,7 +180,12 @@ function! FugitiveCommonDir(...) abort
 endfunction
 
 function! FugitiveWorkTree(...) abort
-  return s:Tree(FugitiveGitDir(a:0 ? a:1 : -1))
+  let tree = s:Tree(FugitiveGitDir(a:0 ? a:1 : -1))
+  if tree isnot# 0 || a:0 > 1
+    return tree
+  else
+    return ''
+  endif
 endfunction
 
 function! FugitiveIsGitDir(path) abort
@@ -204,9 +209,14 @@ function! s:Tree(path) abort
     let config_file = dir . '/config'
     if filereadable(config_file)
       let config = readfile(config_file,'',10)
-      call filter(config,'v:val =~# "^\\s*worktree *="')
-      if len(config) == 1
+      let wt_config = filter(copy(config),'v:val =~# "^\\s*worktree *="')
+      if len(wt_config) == 1
         let worktree = FugitiveVimPath(matchstr(config[0], '= *\zs.*'))
+      else
+        call filter(config,'v:val =~# "^\\s*bare *= *false *$"')
+        if len(config)
+          let s:worktree_for_dir[dir] = 0
+        endif
       endif
     elseif filereadable(dir . '/gitdir')
       let worktree = fnamemodify(FugitiveVimPath(readfile(dir . '/gitdir')[0]), ':h')
@@ -358,7 +368,7 @@ function! s:ProjectionistDetect() abort
   if empty(base)
     let base = s:Tree(dir)
   endif
-  if len(base)
+  if !empty(base)
     if exists('+shellslash') && !&shellslash
       let base = tr(base, '/', '\')
     endif

syntax/fugitive.vim

@@ -8,7 +8,7 @@ syn spell notoplevel
 syn include @fugitiveDiff syntax/diff.vim
 
 syn match fugitiveHeader /^[A-Z][a-z][^:]*:/ nextgroup=fugitiveHash,fugitiveSymbolicRef skipwhite
-syn match fugitiveBareHeader /^Bare:/
+syn match fugitiveHeader /^Bare:\|^Warning:\|^Error:/
 syn match fugitiveHelpHeader /^Help:/ nextgroup=fugitiveHelpTag skipwhite
 syn match fugitiveHelpTag    /\S\+/ contained
 
@@ -36,7 +36,6 @@ for s:section in ['Untracked', 'Unstaged', 'Staged']
 endfor
 unlet s:section
 
-hi def link fugitiveBareHeader fugitiveHeader
 hi def link fugitiveHelpHeader fugitiveHeader
 hi def link fugitiveHeader Label
 hi def link fugitiveHelpTag Tag