patch 8.0.0420: text garbled when the system encoding differs from 'encoding'

Problem:    When running :make the output may be in the system encoding,
            different from 'encoding'.
Solution:   Add the 'makeencoding' option. (Ken Takata)

src/testdir/test_makeencoding.vim

@@ -0,0 +1,106 @@
+" Tests for 'makeencoding'.
+if !has('multi_byte')
+  finish
+endif
+
+source shared.vim
+
+let s:python = PythonProg()
+if s:python == ''
+  " Can't run this test.
+  finish
+endif
+
+let s:script = 'test_makeencoding.py'
+
+let s:message_tbl = {
+      \ 'utf-8': 'ÀÈÌÒÙ こんにちは 你好',
+      \ 'latin1': 'ÀÈÌÒÙ',
+      \ 'cp932': 'こんにちは',
+      \ 'cp936': '你好',
+      \}
+
+
+" Tests for :cgetfile and :lgetfile.
+func Test_getfile()
+  set errorfile=Xerror.txt
+  set errorformat=%f(%l)\ :\ %m
+
+  " :cgetfile
+  for enc in keys(s:message_tbl)
+    let &makeencoding = enc
+    exec "silent !" . s:python . " " . s:script . " " . enc . " > " . &errorfile
+    cgetfile
+    copen
+    call assert_equal("Xfoobar.c|10| " . s:message_tbl[enc] . " (" . enc . ")",
+          \ getline('.'))
+    cclose
+  endfor
+
+  " :lgetfile
+  for enc in keys(s:message_tbl)
+    let &makeencoding = enc
+    exec "silent !" . s:python . " " . s:script . " " . enc . " > " . &errorfile
+    lgetfile
+    lopen
+    call assert_equal("Xfoobar.c|10| " . s:message_tbl[enc] . " (" . enc . ")",
+          \ getline('.'))
+    lclose
+  endfor
+
+  call delete(&errorfile)
+endfunc
+
+
+" Tests for :grep and :lgrep.
+func Test_grep()
+  let &grepprg = s:python
+  set grepformat=%f(%l)\ :\ %m
+
+  " :grep
+  for enc in keys(s:message_tbl)
+    let &makeencoding = enc
+    exec "silent grep! " . s:script . " " . enc
+    copen
+    call assert_equal("Xfoobar.c|10| " . s:message_tbl[enc] . " (" . enc . ")",
+          \ getline('.'))
+    cclose
+  endfor
+
+  " :lgrep
+  for enc in keys(s:message_tbl)
+    let &makeencoding = enc
+    exec "silent lgrep! " . s:script . " " . enc
+    lopen
+    call assert_equal("Xfoobar.c|10| " . s:message_tbl[enc] . " (" . enc . ")",
+          \ getline('.'))
+    lclose
+  endfor
+endfunc
+
+
+" Tests for :make and :lmake.
+func Test_make()
+  let &makeprg = s:python
+  set errorformat=%f(%l)\ :\ %m
+
+  " :make
+  for enc in keys(s:message_tbl)
+    let &makeencoding = enc
+    exec "silent make! " . s:script . " " . enc
+    copen
+    call assert_equal("Xfoobar.c|10| " . s:message_tbl[enc] . " (" . enc . ")",
+          \ getline('.'))
+    cclose
+  endfor
+
+  " :lmake
+  for enc in keys(s:message_tbl)
+    let &makeencoding = enc
+    exec "silent lmake! " . s:script . " " . enc
+    lopen
+    call assert_equal("Xfoobar.c|10| " . s:message_tbl[enc] . " (" . enc . ")",
+          \ getline('.'))
+    lclose
+  endfor
+endfunc