Pass absolute paths through FugitiveGenerate() unchanged

This is designed to exclude traditional paths, URLs, and also Vim
constructs like zipfile:c:\foo.zip::file.

autoload/fugitive.vim

@@ -337,8 +337,8 @@ function! s:repo_translate(spec, ...) dict abort
     let f = dir . s:sub(rev, '^/=\.git', '')
   elseif empty(rev) || rev ==# '/.'
     return self.tree()
-  elseif rev =~# '^/'
-    let f = self.tree(rev)
+  elseif rev =~# '^\.\=/'
+    let f = self.tree(substitute(rev, '^\.', '', ''))
   elseif rev =~# '^:[0-3]:/\@!'
     let f = 'fugitive://' . dir . '//' . rev[1] . '/' . rev[3:-1]
   elseif rev ==# ':'
@@ -532,8 +532,10 @@ function! fugitive#Path(url, ...) abort
     let file = '/.git'.url[strlen(dir) : -1]
   elseif len(tree) && s:cpath(url[0 : len(tree)]) ==# s:cpath(tree . '/')
     let file = url[len(tree) : -1]
+  elseif s:cpath(url) ==# s:cpath(tree)
+    let file = '/'
   endif
-  if empty(file) && a:1 ==# ''
+  if empty(file) && a:1 =~# '^\%([.:]\=/\)\=$'
     return s:shellslash(fugitive#Real(a:url))
   endif
   return substitute(file, '^/', a:1, '')

doc/fugitive.txt

@@ -323,7 +323,7 @@ refs/heads/x    .git/refs/heads/x
 @               The commit referenced by @ aka HEAD
 master^         The parent of the commit referenced by master
 master:         The tree referenced by master
-/master         The file named master in the work tree
+./master        The file named master in the work tree
 Makefile        The file named Makefile in the work tree
 @^:Makefile     The file named Makefile in the parent of HEAD
 :Makefile       The file named Makefile in the index (writable)
@@ -335,7 +335,6 @@ Makefile        The file named Makefile in the work tree
 :1              The current file's common ancestor during a conflict
 :2              The current file in the target branch during a conflict
 :3              The current file in the merged branch during a conflict
-:/foo           The most recent commit with "foo" in the message
 
 STATUSLINE                                      *fugitive-statusline*
 

plugin/fugitive.vim

@@ -159,6 +159,9 @@ function! FugitivePath(...) abort
 endfunction
 
 function! FugitiveGenerate(...) abort
+  if a:0 && s:shellslash(a:0) =~# '^\%(\a\a\+:\)\=\%(a:\)\=/\|^[~$]'
+    return a:1
+  endif
   return fugitive#repo(a:0 > 1 ? a:2 : get(b:, 'git_dir', '')).translate(a:0 ? a:1 : '', 1)
 endfunction