Use postStartCommand to avoid creating a .gitconfig (#1391)

Use postStartCommand to avoid creating a new .gitconfig

Author: chrmarti

src/common-utils/README.md

@@ -38,7 +38,7 @@ these images have already allocated UID & GID 1000. Attempting to add this Featu
 
 By default, this script provides a custom command prompt that includes information about the git repository for the current folder. However, with certain large repositories, this can result in a slow command prompt due to the performance of needed git operations.
 
-For performance reasons, a "dirty" indicator that tells you whether or not there are uncommitted changes is disabled by default. You can opt to turn this on for smaller repositories by entering the following in a terminal or adding it to your `postCreateCommand`:
+For performance reasons, a "dirty" indicator that tells you whether or not there are uncommitted changes is disabled by default. You can opt to turn this on for smaller repositories by entering the following in a terminal or adding it to your `postStartCommand`:
 
 ```bash
 git config devcontainers-theme.show-dirty 1