fix system call handling on windows (#575)

- ensure that all system calls go via installer.vim
  (vundle#installer#system, used to be s:system)
- escape/wrap complex command sequences
- log commands before trying to execute them

autoload/vundle/installer.vim

@@ -287,7 +287,7 @@ func! vundle#installer#delete(bang, dir_name) abort
   let bundle = vundle#config#init_bundle(a:dir_name, {})
   let cmd .= ' '.vundle#installer#shellesc(bundle.path())
 
-  let out = s:system(cmd)
+  let out = vundle#installer#system(cmd)
 
   call s:log('')
   call s:log('Plugin '.a:dir_name)
@@ -347,7 +347,7 @@ endf
 func! s:get_current_origin_url(bundle) abort
   let cmd = 'cd '.vundle#installer#shellesc(a:bundle.path()).' && git config --get remote.origin.url'
   let cmd = vundle#installer#shellesc_cd(cmd)
-  let out = s:strip(s:system(cmd))
+  let out = s:strip(vundle#installer#system(cmd))
   return out
 endf
 
@@ -361,7 +361,7 @@ endf
 func! s:get_current_sha(bundle)
   let cmd = 'cd '.vundle#installer#shellesc(a:bundle.path()).' && git rev-parse HEAD'
   let cmd = vundle#installer#shellesc_cd(cmd)
-  let out = s:system(cmd)[0:15]
+  let out = vundle#installer#system(cmd)[0:15]
   return out
 endf
 
@@ -448,10 +448,10 @@ func! s:sync(bang, bundle) abort
       return 'todate'
   endif
 
-  let out = s:system(cmd)
   call s:log('')
   call s:log('Plugin '.a:bundle.name_spec)
   call s:log(cmd, '$ ')
+  let out = vundle#installer#system(cmd)
   call s:log(out, '> ')
 
   if 0 != v:shell_error
@@ -512,8 +512,14 @@ endf
 " cmd    -- the command passed to system() (string)
 " return -- the return value from system()
 " ---------------------------------------------------------------------------
-func! s:system(cmd) abort
-  return system(a:cmd)
+func! vundle#installer#system(cmd) abort
+  " would this suffice?
+  " return system('"'.a:cmd.'"')
+  let slash = &shellslash
+  set noshellslash
+  let result = system(shellescape(a:cmd))
+  if slash | set shellslash | endif
+  return result
 endf
 
 

autoload/vundle/scripts.vim

@@ -85,7 +85,7 @@ func! s:create_changelog() abort
 
     let cmd = vundle#installer#shellesc_cd(cmd)
 
-    let updates = system(cmd)
+    let updates = vundle#installer#system(cmd)
 
     call add(changelog, '')
     call add(changelog, 'Updated Plugin: '.bundle.name)
@@ -239,7 +239,7 @@ func! s:fetch_scripts(to)
     return 1
   endif
 
-  call system(cmd)
+  call vundle#installer#system(cmd)
 
   if (0 != v:shell_error)
     echoerr 'Error fetching scripts!'