Add test and fix Exec() call

Author: arp242

autoload/go/tool.vim

@@ -170,7 +170,7 @@ function! go#tool#ExecuteInDir(cmd) abort
   " that don't actually exist on the file system (e.g. vim-fugitive's
   " GitDiff).
   if !isdirectory(expand("%:p:h"))
-    let out = go#util#Exec("false")
+    let [out, err] = go#util#Exec(["false"])
     return out
   endif
 

autoload/go/tool_test.vim

@@ -0,0 +1,21 @@
+func! Test_ExecuteInDir() abort
+  let l:tmp = gotest#write_file('a/a.go', ['package a'])
+  try
+    let l:out = go#tool#ExecuteInDir("pwd")
+    call assert_equal(l:tmp . "/src/a\n", l:out)
+  finally
+    call delete(l:tmp, 'rf')
+  endtry
+endfunc
+
+func! Test_ExecuteInDir_nodir() abort
+  let l:tmp = go#util#tempdir("executeindir")
+  exe ':e ' . l:tmp . '/new-dir/a'
+
+  try
+    let l:out = go#tool#ExecuteInDir("pwd")
+    call assert_equal('', l:out)
+  finally
+    call delete(l:tmp, 'rf')
+  endtry
+endfunc