Unify :G and :Git

The principle difference between these two is that :G uses -bar while
:Git fakes it.  Faking it enables double quotes, but I don't really
trust it.

autoload/fugitive.vim

@@ -1430,10 +1430,6 @@ function! fugitive#CompleteObject(base, ...) abort
   return map(entries, 's:fnameescape(v:val)')
 endfunction
 
-function! fugitive#Complete(...) abort
-  return call('fugitive#CompleteObject', a:000)
-endfunction
-
 " Section: Buffer auto-commands
 
 function! s:ReplaceCmd(cmd) abort
@@ -1961,23 +1957,36 @@ augroup END
 " Section: :Git
 
 call s:command("-bang -nargs=? -range=-1 -complete=customlist,fugitive#CompleteGit Git", "Git")
+call s:command("-bar -bang -range=-1 -nargs=* -complete=customlist,fugitive#CompleteGit G", "")
+
+function! s:GitExec(line1, line2, range, count, bang, mods, reg, args, dir) abort
+  if empty(a:args)
+    return s:StatusCommand(a:line1, a:line2, a:range, a:count, a:bang, a:mods, a:reg, '', [])
+  endif
+  if a:bang
+    return s:OpenExec((a:count > 0 ? a:count : '') . (a:count ? 'split' : 'edit'), a:mods, a:args, a:dir)
+  endif
+  let git = s:UserCommandList(a:dir)
+  if has('gui_running') && !has('win32')
+    call add(git, '--no-pager')
+  endif
+  let pre = ''
+  if has('nvim') && executable('env')
+    let pre .= 'env GIT_TERMINAL_PROMPT=0 '
+  endif
+  return 'exe ' . string('!' . escape(pre . s:shellesc(git + a:args), '!#%'))
+endfunction
 
 function! s:GitCommand(line1, line2, range, count, bang, mods, reg, arg, args) abort
   let dir = s:Dir()
-  let tree = s:Tree(dir)
+  let [args, after] = s:SplitExpandChain(a:arg, s:Tree(dir))
-  let [args, after] = s:SplitExpandChain(a:arg, tree)
+  return s:GitExec(a:line1, a:line2, a:range, a:count, a:bang, a:mods, a:reg, args, dir) . after
-  if a:bang
+endfunction
-    return s:OpenExec((a:count > 0 ? a:count : '') . (a:count ? 'split' : 'edit'), a:mods, args, dir) . after
+
-  endif
+function! s:Command(line1, line2, range, count, bang, mods, reg, arg, args, ...) abort
-  let git = s:UserCommand(dir)
+  let dir = a:0 ? s:Dir(a:1) : s:Dir()
-  if has('gui_running') && !has('win32')
+  let args = s:SplitExpand(a:arg, s:Tree(dir))
-    let git .= ' --no-pager'
+  return s:GitExec(a:line1, a:line2, a:range, a:count, a:bang, a:mods, a:reg, args, dir)
-  endif
-  if has('nvim') && executable('env')
-    let git = 'env GIT_TERMINAL_PROMPT=0 ' . git
-  endif
-  let cmd = "exe '!'.escape(" . string(git . ' ' . s:shellesc(args)) . ",'!#%')"
-  return cmd . after
 endfunction
 
 let s:exec_paths = {}
@@ -2017,6 +2026,10 @@ function! fugitive#CompleteGit(lead, ...) abort
   return filter(results, 'strpart(v:val, 0, strlen(a:lead)) ==# a:lead')
 endfunction
 
+function! fugitive#Complete(...) abort
+  return call('fugitive#CompleteGit', a:000)
+endfunction
+
 " Section: :Gcd, :Glcd
 
 function! s:DirComplete(A, L, P) abort
@@ -2038,7 +2051,6 @@ call s:command("-bar -bang -nargs=? -complete=customlist,s:DirComplete Glcd :exe
 " Section: :Gstatus
 
 call s:command("-bar -bang -range=-1 Gstatus", "Status")
-call s:command("-bar -bang -range=-1 G", "Status")
 
 function! s:StatusCommand(line1, line2, range, count, bang, mods, reg, arg, args, ...) abort
   let dir = a:0 ? a:1 : s:Dir()

doc/fugitive.txt

@@ -15,12 +15,16 @@ COMMANDS                                        *fugitive-commands*
 These commands are local to the buffers in which they work (generally, buffers
 that are part of Git repositories).
 
+                                        *fugitive-:G* *fugitive-:Gstatus*
+:G                      Bring up a summary window vaguely akin to git-status.
+:Gstatus                Press g? or see |fugitive-mappings| for usage.
+
                                                 *fugitive-:Git*
-:Git [args]             Run an arbitrary git command. Similar to :!git [args]
+:Git {args}             Run an arbitrary git command. Similar to :!git [args]
-                        but chdir to the repository tree first.
+:G {args}               but chdir to the repository tree first.
 
                                                 *fugitive-:Git!*
-:Git! [args]            Like |:Git|, but capture the output into a temp file,
+:Git! {args}            Like |:Git|, but capture the output into a temp file,
                         and |:split| that that temp file.  Use :0Git to
                         |:edit| the temp file instead.
 
@@ -30,10 +34,6 @@ that are part of Git repositories).
                                                 *fugitive-:Glcd*
 :Glcd [directory]       |:lcd| relative to the repository.
 
-                                        *fugitive-:Gstatus* *fugitive-:G*
-:G                      Bring up a summary window vaguely akin to git-status.
-:Gstatus                Press g? or see |fugitive-mappings| for usage.
-
                                                 *fugitive-:Gcommit*
 :Gcommit [args]         A wrapper around git-commit.  Unless the arguments
                         given would skip the invocation of an editor (e.g.,