Keep track of the default branch of the origin (#1272)

Fix #1005

vim-plug will now run `git remote set-head origin -a` on PlugUpdate to
keep track of the default branch of the origin, so that it can still
update a plugin even if its default branch has changed.

This additional command will slow down the update process, but this is
an unavoidable price to pay for the correctness of the task. However,
vim-plug will run checkout and merge commands in parallel, so this
improvement will slightly offset the slowdown.

plug.vim

@@ -1106,12 +1106,14 @@ endfunction
 function! s:checkout(spec)
   let sha = a:spec.commit
   let output = s:git_revision(a:spec.dir)
+  let error = 0
   if !empty(output) && !s:hash_match(sha, s:lines(output)[0])
     let credential_helper = s:git_version_requirement(2) ? '-c credential.helper= ' : ''
     let output = s:system(
           \ 'git '.credential_helper.'fetch --depth 999999 && git checkout '.plug#shellescape(sha).' --', a:spec.dir)
+    let error = v:shell_error
   endif
-  return output
+  return [output, error]
 endfunction
 
 function! s:finish(pull)
@@ -1172,7 +1174,7 @@ function! s:update_impl(pull, force, args) abort
   let threads = (len(args) > 0 && args[-1] =~ '^[1-9][0-9]*$') ?
                   \ remove(args, -1) : get(g:, 'plug_threads', 16)
 
-  let managed = filter(copy(g:plugs), 's:is_managed(v:key)')
+  let managed = filter(deepcopy(g:plugs), 's:is_managed(v:key)')
   let todo = empty(args) ? filter(managed, '!v:val.frozen || !isdirectory(v:val.dir)') :
                          \ filter(managed, 'index(args, v:key) >= 0')
 
@@ -1306,9 +1308,11 @@ function! s:update_finish()
       if !pos
         continue
       endif
+      let out = ''
+      let error = 0
       if has_key(spec, 'commit')
         call s:log4(name, 'Checking out '.spec.commit)
-        let out = s:checkout(spec)
+        let [out, error] = s:checkout(spec)
       elseif has_key(spec, 'tag')
         let tag = spec.tag
         if tag =~ '\*'
@@ -1321,19 +1325,16 @@ function! s:update_finish()
         endif
         call s:log4(name, 'Checking out '.tag)
         let out = s:system('git checkout -q '.plug#shellescape(tag).' -- 2>&1', spec.dir)
-      else
+        let error = v:shell_error
-        let branch = s:git_origin_branch(spec)
-        call s:log4(name, 'Merging origin/'.s:esc(branch))
-        let out = s:system('git checkout -q '.plug#shellescape(branch).' -- 2>&1'
-              \. (has_key(s:update.new, name) ? '' : ('&& git merge --ff-only '.plug#shellescape('origin/'.branch).' 2>&1')), spec.dir)
       endif
-      if !v:shell_error && filereadable(spec.dir.'/.gitmodules') &&
+      if !error && filereadable(spec.dir.'/.gitmodules') &&
             \ (s:update.force || has_key(s:update.new, name) || s:is_updated(spec.dir))
         call s:log4(name, 'Updating submodules. This may take a while.')
         let out .= s:bang('git submodule update --init --recursive'.s:submodule_opt.' 2>&1', spec.dir)
+        let error = v:shell_error
       endif
       let msg = s:format_message(v:shell_error ? 'x': '-', name, out)
-      if v:shell_error
+      if error
         call add(s:update.errors, name)
         call s:regress_bar()
         silent execute pos 'd _'
@@ -1396,7 +1397,9 @@ function! s:job_out_cb(self, data) abort
   if !self.running || self.tick % len(s:jobs) == 0
     let bullet = self.running ? (self.new ? '+' : '*') : (self.error ? 'x' : '-')
     let result = self.error ? join(self.lines, "\n") : s:last_non_empty_line(self.lines)
-    call s:log(bullet, self.name, result)
+    if len(result)
+      call s:log(bullet, self.name, result)
+    endif
   endif
 endfunction
 
@@ -1420,16 +1423,17 @@ function! s:nvim_cb(job_id, data, event) dict abort
     \ s:job_cb('s:job_exit_cb', self, 0, a:data)
 endfunction
 
-function! s:spawn(name, cmd, opts)
+function! s:spawn(name, spec, queue, opts)
-  let job = { 'name': a:name, 'running': 1, 'error': 0, 'lines': [''],
+  let job = { 'name': a:name, 'spec': a:spec, 'running': 1, 'error': 0, 'lines': [''],
-            \ 'new': get(a:opts, 'new', 0) }
+            \ 'new': get(a:opts, 'new', 0), 'queue': copy(a:queue) }
+  let Item = remove(job.queue, 0)
+  let argv = type(Item) == s:TYPE.funcref ? call(Item, [a:spec]) : Item
   let s:jobs[a:name] = job
 
   if s:nvim
     if has_key(a:opts, 'dir')
       let job.cwd = a:opts.dir
     endif
-    let argv = a:cmd
     call extend(job, {
     \ 'on_stdout': function('s:nvim_cb'),
     \ 'on_stderr': function('s:nvim_cb'),
@@ -1445,7 +1449,7 @@ function! s:spawn(name, cmd, opts)
             \ 'Invalid arguments (or job table is full)']
     endif
   elseif s:vim8
-    let cmd = join(map(copy(a:cmd), 'plug#shellescape(v:val, {"script": 0})'))
+    let cmd = join(map(copy(argv), 'plug#shellescape(v:val, {"script": 0})'))
     if has_key(a:opts, 'dir')
       let cmd = s:with_cd(cmd, a:opts.dir, 0)
     endif
@@ -1465,27 +1469,34 @@ function! s:spawn(name, cmd, opts)
       let job.lines   = ['Failed to start job']
     endif
   else
-    let job.lines = s:lines(call('s:system', has_key(a:opts, 'dir') ? [a:cmd, a:opts.dir] : [a:cmd]))
+    let job.lines = s:lines(call('s:system', has_key(a:opts, 'dir') ? [argv, a:opts.dir] : [argv]))
     let job.error = v:shell_error != 0
     let job.running = 0
   endif
 endfunction
 
 function! s:reap(name)
-  let job = s:jobs[a:name]
+  let job = remove(s:jobs, a:name)
   if job.error
     call add(s:update.errors, a:name)
   elseif get(job, 'new', 0)
     let s:update.new[a:name] = 1
   endif
-  let s:update.bar .= job.error ? 'x' : '='
 
-  let bullet = job.error ? 'x' : '-'
+  let more = len(get(job, 'queue', []))
+  let bullet = job.error ? 'x' : more ? (job.new ? '+' : '*') : '-'
   let result = job.error ? join(job.lines, "\n") : s:last_non_empty_line(job.lines)
-  call s:log(bullet, a:name, empty(result) ? 'OK' : result)
+  if len(result)
-  call s:bar()
+    call s:log(bullet, a:name, result)
+  endif
 
-  call remove(s:jobs, a:name)
+  if !job.error && more
+    let job.spec.queue = job.queue
+    let s:update.todo[a:name] = job.spec
+  else
+    let s:update.bar .= job.error ? 'x' : '='
+    call s:bar()
+  endif
 endfunction
 
 function! s:bar()
@@ -1538,6 +1549,16 @@ function! s:update_vim()
   call s:tick()
 endfunction
 
+function! s:checkout_command(spec)
+  let a:spec.branch = s:git_origin_branch(a:spec)
+  return ['git', 'checkout', '-q', a:spec.branch, '--']
+endfunction
+
+function! s:merge_command(spec)
+  let a:spec.branch = s:git_origin_branch(a:spec)
+  return ['git', 'merge', '--ff-only', 'origin/'.a:spec.branch]
+endfunction
+
 function! s:tick()
   let pull = s:update.pull
   let prog = s:progress_opt(s:nvim || s:vim8)
@@ -1552,13 +1573,18 @@ while 1 " Without TCO, Vim stack is bound to explode
 
   let name = keys(s:update.todo)[0]
   let spec = remove(s:update.todo, name)
-  let new  = empty(globpath(spec.dir, '.git', 1))
+  let queue = get(spec, 'queue', [])
+  let new = empty(globpath(spec.dir, '.git', 1))
 
-  call s:log(new ? '+' : '*', name, pull ? 'Updating ...' : 'Installing ...')
+  if empty(queue)
-  redraw
+    call s:log(new ? '+' : '*', name, pull ? 'Updating ...' : 'Installing ...')
+    redraw
+  endif
 
   let has_tag = has_key(spec, 'tag')
-  if !new
+  if len(queue)
+    call s:spawn(name, spec, queue, { 'dir': spec.dir })
+  elseif !new
     let [error, _] = s:git_validate(spec, 0)
     if empty(error)
       if pull
@@ -1569,7 +1595,11 @@ while 1 " Without TCO, Vim stack is bound to explode
         if !empty(prog)
           call add(cmd, prog)
         endif
-        call s:spawn(name, cmd, { 'dir': spec.dir })
+        let queue = [cmd, split('git remote set-head origin -a')]
+        if !has_tag && !has_key(spec, 'commit')
+          call extend(queue, [function('s:checkout_command'), function('s:merge_command')])
+        endif
+        call s:spawn(name, spec, queue, { 'dir': spec.dir })
       else
         let s:jobs[name] = { 'running': 0, 'lines': ['Already installed'], 'error': 0 }
       endif
@@ -1584,7 +1614,7 @@ while 1 " Without TCO, Vim stack is bound to explode
     if !empty(prog)
       call add(cmd, prog)
     endif
-    call s:spawn(name, extend(cmd, [spec.uri, s:trim(spec.dir)]), { 'new': 1 })
+    call s:spawn(name, spec, [extend(cmd, [spec.uri, s:trim(spec.dir)]), function('s:checkout_command'), function('s:merge_command')], { 'new': 1 })
   endif
 
   if !s:jobs[name].running

test/workflow.vader

@@ -983,7 +983,8 @@ Execute (PlugInstall!):
   Assert filereadable(g:plugs['vim-easy-align'].dir.'/installed2'),
     \ 'vim-easy-align/installed2 should exist'
   AssertEqual '7f8cd78cb1fe52185b98b16a3749811f0cc508af', GitCommit('vim-pseudocl')
-  AssertEqual 'no-t_co', GitBranch('seoul256.vim')
+  " Was updated to the default branch of origin by previous PlugUpdate
+  AssertEqual 'master', GitBranch('seoul256.vim')
   AssertEqual '1.5.3', GitTag('goyo.vim')
 
 Execute (When submodules are not initialized):