Fix race conditions generating sequencer sections

Resolves: https://github.com/tpope/vim-fugitive/issues/2411

LICENSE

@@ -1,81 +0,0 @@
-VIM LICENSE
-
-I)  There are no restrictions on distributing unmodified copies of
-    fugitive.vim except that they must include this license text.  You can
-    also distribute unmodified parts of fugitive.vim, likewise unrestricted
-    except that they must include this license text.  You are also allowed to
-    include executables that you made from the unmodified fugitive.vim
-    sources, plus your own usage examples and Vim scripts.
-
-II) It is allowed to distribute a modified (or extended) version of
-    fugitive.vim, including executables and/or source code, when the following
-    four conditions are met:
-    1) This license text must be included unmodified.
-    2) The modified fugitive.vim must be distributed in one of the following
-       five ways:
-       a) If you make changes to fugitive.vim yourself, you must clearly
-          describe in the distribution how to contact you.  When the
-          maintainer asks you (in any way) for a copy of the modified
-          fugitive.vim you distributed, you must make your changes, including
-          source code, available to the maintainer without fee.  The
-          maintainer reserves the right to include your changes in the
-          official version of fugitive.vim.  What the maintainer will do with
-          your changes and under what license they will be distributed is
-          negotiable.  If there has been no negotiation then this license, or
-          a later version, also applies to your changes. The current
-          maintainer is Bram Moolenaar <Bram@vim.org>.  If this changes it
-          will be announced in appropriate places (most likely vim.sf.net,
-          www.vim.org and/or comp.editors). When it is completely impossible
-          to contact the maintainer, the obligation to send him your changes
-          ceases.  Once the maintainer has confirmed that he has received your
-          changes they will not have to be sent again.
-       b) If you have received a modified fugitive.vim that was distributed as
-          mentioned under a) you are allowed to further distribute it
-          unmodified, as mentioned at I).  If you make additional changes the
-          text under a) applies to those changes.
-       c) Provide all the changes, including source code, with every copy of
-          the modified fugitive.vim you distribute.  This may be done in the
-          form of a context diff.  You can choose what license to use for new
-          code you add.  The changes and their license must not restrict
-          others from making their own changes to the official version of
-          fugitive.vim.
-       d) When you have a modified fugitive.vim which includes changes as
-          mentioned under c), you can distribute it without the source code
-          for the changes if the following three conditions are met:
-          - The license that applies to the changes permits you to distribute
-            the changes to the Vim maintainer without fee or restriction, and
-            permits the Vim maintainer to include the changes in the official
-            version of fugitive.vim without fee or restriction.
-          - You keep the changes for at least three years after last
-            distributing the corresponding modified fugitive.vim.  When the
-            maintainer or someone who you distributed the modified
-            fugitive.vim to asks you (in any way) for the changes within this
-            period, you must make them available to him.
-          - You clearly describe in the distribution how to contact you.  This
-            contact information must remain valid for at least three years
-            after last distributing the corresponding modified fugitive.vim,
-            or as long as possible.
-       e) When the GNU General Public License (GPL) applies to the changes,
-          you can distribute the modified fugitive.vim under the GNU GPL
-          version 2 or any later version.
-    3) A message must be added, at least in the output of the ":version"
-       command and in the intro screen, such that the user of the modified
-       fugitive.vim is able to see that it was modified.  When distributing as
-       mentioned under 2)e) adding the message is only required for as far as
-       this does not conflict with the license used for the changes.
-    4) The contact information as required under 2)a) and 2)d) must not be
-       removed or changed, except that the person himself can make
-       corrections.
-
-III) If you distribute a modified version of fugitive.vim, you are encouraged
-     to use the Vim license for your changes and make them available to the
-     maintainer, including the source code.  The preferred way to do this is
-     by e-mail or by uploading the files to a server and e-mailing the URL. If
-     the number of changes is small (e.g., a modified Makefile) e-mailing a
-     context diff will do.  The e-mail address to be used is
-     <maintainer@vim.org>
-
-IV)  It is not allowed to remove this license from the distribution of the
-     fugitive.vim sources, parts of it or from a modified version.  You may
-     use this license for previous fugitive.vim releases instead of the
-     license that they came with, at your option.

autoload/fugitive.vim

@@ -4,11 +4,6 @@
 " The functions contained within this file are for internal use only.  For the
 " official API, see the commented functions in plugin/fugitive.vim.
 
-if exists('g:autoloaded_fugitive')
-  finish
-endif
-let g:autoloaded_fugitive = 1
-
 " Section: Utility
 
 function! s:function(name) abort
@@ -2071,6 +2066,8 @@ function! s:Expand(rev, ...) abort
     endif
   elseif s:Slash(a:rev) =~# '^\a\a\+://'
     let file = substitute(a:rev, '\\\@<!\%(#\a\|%\x\x\)', '\\&', 'g')
+  elseif a:rev =~# '^:[!#%$]'
+    let file = ':0' . a:rev
   else
     let file = a:rev
   endif
@@ -2697,7 +2694,7 @@ function! s:MapStatus() abort
   call s:MapMotion('gP', "exe <SID>StageJump(v:count, 'Unpulled')")
   call s:MapMotion('gr', "exe <SID>StageJump(v:count, 'Rebasing')")
   call s:Map('n', 'C', ":echoerr 'fugitive: C has been removed in favor of cc'<CR>", '<silent><unique>')
-  call s:Map('n', 'a', ":<C-U>execute <SID>Do('Toggle',0)<CR>", '<silent>')
+  call s:Map('n', 'a', ":echoerr 'fugitive: a has been removed in favor of s'<CR>", '<silent><unique>')
   call s:Map('n', 'i', ":<C-U>execute <SID>NextExpandedHunk(v:count1)<CR>", '<silent>')
   call s:Map('n', "=", ":<C-U>execute <SID>StageInline('toggle',line('.'),v:count)<CR>", '<silent>')
   call s:Map('n', "<", ":<C-U>execute <SID>StageInline('hide',  line('.'),v:count)<CR>", '<silent>')
@@ -2940,20 +2937,34 @@ function! s:StatusRender(stat) abort
     endif
 
     let sequencing = []
-    if filereadable(fugitive#Find('.git/sequencer/todo', dir))
-      for line in reverse(readfile(fugitive#Find('.git/sequencer/todo', dir)))
+    try
+      let sequencer_todo = reverse(readfile(fugitive#Find('.git/sequencer/todo', dir)))
+    catch
+    endtry
+    if exists('sequencer_todo')
+      for line in sequencer_todo
         let match = matchlist(line, '^\(\l\+\)\s\+\(\x\{4,\}\)\s\+\(.*\)')
         if len(match) && match[1] !~# 'exec\|merge\|label'
           call add(sequencing, {'type': 'Rebase', 'status': get(s:rebase_abbrevs, match[1], match[1]), 'commit': match[2], 'subject': match[3]})
         endif
       endfor
-    elseif filereadable(fugitive#Find('.git/MERGE_MSG', dir))
+    else
+      try
+        let merge_msg = get(readfile(fugitive#Find('.git/MERGE_MSG', dir)), 0, '')
+      catch
+      endtry
+    endif
+    if exists('merge_msg')
       if filereadable(fugitive#Find('.git/CHERRY_PICK_HEAD', dir))
         let pick_head = fugitive#Execute(['rev-parse', '--short', 'CHERRY_PICK_HEAD', '--'], dir).stdout[0]
-        call add(sequencing, {'type': 'Rebase', 'status': 'pick', 'commit': pick_head, 'subject': get(readfile(fugitive#Find('.git/MERGE_MSG', dir)), 0, '')})
+        if !empty(pick_head)
+          call add(sequencing, {'type': 'Rebase', 'status': 'pick', 'commit': pick_head, 'subject': merge_msg})
+        endif
       elseif filereadable(fugitive#Find('.git/REVERT_HEAD', dir))
         let pick_head = fugitive#Execute(['rev-parse', '--short', 'REVERT_HEAD', '--'], dir).stdout[0]
-        call add(sequencing, {'type': 'Rebase', 'status': 'revert', 'commit': pick_head, 'subject': get(readfile(fugitive#Find('.git/MERGE_MSG', dir)), 0, '')})
+        if !empty(pick_head)
+          call add(sequencing, {'type': 'Rebase', 'status': 'revert', 'commit': pick_head, 'subject': merge_msg})
+        endif
       endif
     endif
 
@@ -2976,7 +2987,7 @@ function! s:StatusRender(stat) abort
     endif
 
     call s:AddSection(to, 'Rebasing ' . rebasing_head, rebasing)
-    call s:AddSection(to, get(get(sequencing, 0, {}), 'tous', '') ==# 'revert' ? 'Reverting' : 'Cherry Picking', sequencing)
+    call s:AddSection(to, get(get(sequencing, 0, {}), 'status', '') ==# 'revert' ? 'Reverting' : 'Cherry Picking', sequencing)
     call s:AddSection(to, 'Untracked', untracked)
     call s:AddDiffSection(to, stat, 'Unstaged', unstaged)
     call s:AddDiffSection(to, stat, 'Staged', staged)
@@ -7435,9 +7446,12 @@ function! s:BrowserOpen(url, mods, echo_copy) abort
   else
     if !exists('g:loaded_netrw')
       runtime! autoload/netrw.vim
+      runtime! autoload/netrw/os.vim
     endif
     if exists('*netrw#Open')
       return 'echo '.string(url).'|' . mods . 'call netrw#Open('.string(url).')'
+    elseif exists('*netrw#os#Open')
+      return 'echo '.string(url).'|' . mods . 'call netrw#os#Open('.string(url).')'
     elseif exists('*netrw#BrowseX')
       return 'echo '.string(url).'|' . mods . 'call netrw#BrowseX('.string(url).', 0)'
     elseif exists('*netrw#NetrwBrowseX')