misc/vim: fix for autocompletion

Vim autocompletion respects the $GOPATH variable and does not
    ignore dashes ('-'), dots ('.') and underscores ('_') like found
    in many remote packages.
    Environment variable $GOROOT is determined by calling
    'go env GOROOT' instead of relying on the user's environment
    variables.

    Fixes #3876
    Fixes #3882

R=golang-dev, franciscossouza, dsymonds, minux.ma
CC=golang-dev
https://golang.org/cl/6443151

misc/vim/autoload/go/complete.vim

@@ -29,13 +29,34 @@ if len(s:goarch) == 0
 endif
 
 function! go#complete#Package(ArgLead, CmdLine, CursorPos)
+  let dirs = []
+
+  if executable('go')
+      let goroot = substitute(system('go env GOROOT'), '\n', '', 'g')
+      if v:shell_error
+          echo '\'go env GOROOT\' failed'
+      endif
+  else
       let goroot = $GOROOT
-  if len(goroot) == 0
-    " should not occur.
+  endif
+
+  if len(goroot) != 0 && isdirectory(goroot)
+    let dirs += [ goroot ]
+  endif
+
+  let workspaces = split($GOPATH, ':')
+  if workspaces != []
+      let dirs += workspaces
+  endif
+
+  if len(dirs) == 0
+      " should not happen
       return []
   endif
+
   let ret = {}
-  let root = expand(goroot.'/pkg/'.s:goos.'_'.s:goarch)
+  for dir in dirs
+    let root = expand(dir . '/pkg/' . s:goos . '_' . s:goarch)
     for i in split(globpath(root, a:ArgLead.'*'), "\n")
       if isdirectory(i)
         let i .= '/'
@@ -45,5 +66,6 @@ function! go#complete#Package(ArgLead, CmdLine, CursorPos)
       let i = substitute(substitute(i[len(root)+1:], '[\\]', '/', 'g'), '\.a$', '', 'g')
       let ret[i] = i
     endfor
+  endfor
   return sort(keys(ret))
 endfunction

misc/vim/plugin/godoc.vim

@@ -72,7 +72,7 @@ function! s:Godoc(...)
   if !len(word)
     let word = expand('<cword>')
   endif
-  let word = substitute(word, '[^a-zA-Z0-9\/]', '', 'g')
+  let word = substitute(word, '[^a-zA-Z0-9\\/._~-]', '', 'g')
   if !len(word)
     return
   endif