Add support for multiple kubeconfig files (#11)

kubectl.zsh

@@ -27,18 +27,23 @@ function() {
 
 add-zsh-hook precmd _zsh_kubectl_prompt_precmd
 function _zsh_kubectl_prompt_precmd() {
-    local kubeconfig updated_at now context namespace ns separator modified_time_fmt
+    local kubeconfig config updated_at now context namespace ns separator modified_time_fmt
 
     kubeconfig="$HOME/.kube/config"
     if [[ -n "$KUBECONFIG" ]]; then
         kubeconfig="$KUBECONFIG"
     fi
 
     zstyle -s ':zsh-kubectl-prompt:' modified_time_fmt modified_time_fmt
-    if ! now="$(stat -L $modified_time_fmt "$kubeconfig" 2>/dev/null)"; then
-        ZSH_KUBECTL_PROMPT="kubeconfig is not found"
-        return 1
-    fi
+
+    # KUBECONFIG environment variable can hold a list of kubeconfig files that is colon-delimited.
+    # Therefore, if KUBECONFIG has been held multiple files, each files need to be checked.
+    while read -d ":" config; do
+        if ! now="${now}$(stat -L $modified_time_fmt "$config" 2>/dev/null)"; then
+            ZSH_KUBECTL_PROMPT="$config doesn't exist"
+            return 1
+        fi
+    done <<< "${kubeconfig}:"
 
     zstyle -s ':zsh-kubectl-prompt:' updated_at updated_at
     if [[ "$updated_at" == "$now" ]]; then