proper automatic go workspace path

shell/go

@@ -1,5 +1,3 @@
-go_commands=(go vim)
-
 _go-installed() {
   which go > /dev/null 2>&1
 }
@@ -7,35 +5,53 @@ _go-installed() {
 _within-go-project() {
   local check_dir=$PWD
   local next_check_dir=${check_dir%/*}
+
   while [ "$next_check_dir" != "" ]; do
     if [ -f "$check_dir/.gopath" ]; then
         echo "$check_dir"
         return
     fi
+
     check_dir="$next_check_dir"
     next_check_dir=${check_dir%/*}
   done
+
   false
 }
 
-_run-with-gopath() {
+_append-go-path() {
+  local bin_path="$*/bin"
+
+  [[ $PATH == *:"$*"* ]] || export PATH="$PATH:$bin_path"
+}
+
+_strip-go-path() {
+  local bin_path="$*/bin"
+
+  [[ $PATH == *":$bin_path"* ]] && export PATH=$(
+    echo -n "$PATH" |
+    awk -v RS=: -v ORS=: '$0=="'"$bin_path"'" {next} {print}' |
+    sed 's/:$//'
+  )
+}
+
+_set-gopath() {
+  export GOPATH="$*"
+}
+
+_unset-gopath() {
+  unset GOPATH
+}
+
+_gopath() {
   local go_path
   if _go-installed && go_path=$(_within-go-project); then
-    env PATH="$PATH:$go_path/bin" GOPATH="$go_path" "$@"
-  else
-    "$@"
+    _set-gopath "$go_path"
+    _append-go-path "$GOPATH"
+  elif [[ -n $GOPATH ]]; then
+    _strip-go-path "$GOPATH"
+    _unset-gopath
   fi
 }
 
-for cmd in "${go_commands[@]}"; do
-  eval "function gopath_$cmd () { _run-with-gopath $cmd \$@; }"
-  alias $cmd=gopath_$cmd
-
-  if [[ -n $ZSH_VERSION ]]; then
-    if which _$cmd > /dev/null 2>&1; then
-      compdef _$cmd gopath_$cmd=$cmd
-    fi
-  fi
-done
-
 # vim: ft=sh