Does TortoiseGit automatically update submodules when switching branches?

No, TortoiseGit does not automatically update submodules when switching branches by default. To achieve a workflow where submodule pointers follow the target branch automatically without manual intervention, you must explicitly enable recursion settings in the interface or global configuration.

The Default Behavior

By default, TortoiseGit (across versions 3.x and 4.x) follows the standard Git behavior where submodules are merely pointers. When you switch branches, the index updates the submodule pointer, but the actual submodule directories remain at the commit they previously occupied. This results in the submodule being marked as "modified" in your status window because the working directory does not match the pointer recorded in the new branch.

How to Enable Automatic Updates

To ensure submodules update automatically during a branch switch, you have two primary methods of configuration:

1. Per-Operation Setting

• Right-click your repository and select TortoiseGit > Switch/Checkout.
• Look for the Recurse into submodules dropdown menu.
• Change the value from None to Yes or On Demand.
• On Demand will only update submodules where the target branch has a different commit recorded, whereas Yes will update all submodules regardless of state.

2. Global Configuration

If you want this behavior to be the standard for all repositories, you can set the global Git configuration, which TortoiseGit will respect:

git config --global submodule.recurse true

Important Limitations and Assumptions

While enabling recursion automates the update, there are several technical nuances to consider:

• Fetching vs. Updating: These settings update the submodules to the specific commit recorded by the parent branch. They do not perform a git fetch to pull the latest code from the submodule's remote branch unless specifically configured to do so.
• Hooks: You cannot reliably use standard post-checkout hooks to automate this within TortoiseGit specifically, as the GUI-based operations do not always trigger hooks in the same way the CLI does.
• Performance: In repositories with dozens of nested submodules, setting recursion to Yes can significantly increase branch-switching time, as Git must verify and checkout every submodule directory.

Verification

To verify your settings are working, switch branches and check the Submodule column in the TortoiseGit Log. If the commit hash matches the expected commit for that branch immediately, the automation is functioning.