Refactor postAttachCommand (#2312)

* Refactor postAttachCommand

* Refactor comment

.devcontainer/devcontainer.json

@@ -19,11 +19,8 @@
   // To access grafana
   "appPort": "3000:3000",
 
-  // Persist zsh history settings below
-  // overwrite HISTFILE to store history file in the named volume defined below
-  // also setting INC_APPEND_HISTORY to immediately flush command history to the file to keep history when rebuilding the devcontainer
-  "postStartCommand": "echo 'export HISTFILE=/commandhistory/.zsh_history' >> /root/.zshrc && echo 'setopt INC_APPEND_HISTORY' >> /root/.zshrc",
   // define named volume to store zsh history file
   "mounts": ["source=zshhistory-named-volume,target=/commandhistory,type=volume"],
-  "postAttachCommand": "mkdir -p /etc/server && ln -s $(pwd)/cmd/agent/core/ngt/sample.yaml /etc/server/config.yaml"
+
+  "postAttachCommand": ["/bin/bash", ".devcontainer/postAttachCommand.sh"]
 }

.devcontainer/postAttachCommand.sh

@@ -0,0 +1,35 @@
+#!/bin/bash -eu
+#
+# This script is executed as postAttachCommand in devcontainer.json
+# This script does...
+# - create symbolic link of config.yaml for easier development
+# - add command history setting to .zshrc to persist history
+#
+
+echo "creating symbolic link of config ZSHRC..."
+
+LINK_TARGET="$(pwd)/cmd/agent/core/ngt/sample.yaml"
+LINK_SRC="/etc/server/config.yaml"
+
+mkdir -p /etc/server
+
+if [ ! -e "$LINK_SRC" ]; then
+    ln -s "$LINK_TARGET" "$LINK_SRC"
+    echo "created symbolic link: $LINK_SRC -> $LINK_TARGET"
+else
+    echo "$LINK_SRC already exists"
+fi
+
+
+echo "adding history setting to .zshrc..."
+
+LINE1="export HISTFILE=/commandhistory/.zsh_history"
+LINE2="setopt INC_APPEND_HISTORY"
+
+ZSHRC="/root/.zshrc"
+
+# write only if those lines don't exist
+grep -qxF "$LINE1" "$ZSHRC" || echo "$LINE1" >> "$ZSHRC"
+grep -qxF "$LINE2" "$ZSHRC" || echo "$LINE2" >> "$ZSHRC"
+
+echo "added history setting to .zshrc"