Why can't I stash submodule changes?

I’m having trouble understanding why I cannot stash changes to a submodule.

When adding a submodule to a repository (`git submodule add ./sub-repo`), I can then run `git stash` and `git stash pop` with expected results—the submodule disappears and reappears in the working tree.

However, when I try stashing an update to a submodule, `git stash` reports “No local changes to save”. The following shell script illustrates this behavior:

# Create repo mkdir test-repo cd test-repo git init git commit --allow-empty -m "Initial commit"

# Create submodule mkdir sub-repo cd sub-repo git init git commit --allow-empty -m "Initial commit" cd -

# Add submodule git submodule add ./sub-repo git commit -m "Add submodule"

# Modify submodule cd sub-repo touch foo git add foo git commit -m "Submodule changed" cd -

# Stash submodule change git stash # <---------------------------Displays "No local changes to save”

I’m trying to wrap my head around why this is the current behavior, as I suspect this is intentional but it seems unexpected. If anyone can shed any light on this, I would really appreciate it!

Thanks,

Shane

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On 4/5/2015 10:15 PM, Shane da Silva wrote:

Why would you expect anything else? You have no local changes ( since you committed them already ). In other words, git status shows no uncommitted changes, so there is nothing to stash.

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Am 06.04.2015 um 04:15 schrieb Shane da Silva:

Just to be sure: Only the index of the superproject and the .gitmodules file are updated by stash to either contain the submodule or not. But the subdirectory "sub-repo" stays unchanged and won't be removed or reappear, right?

Thanks for providing a recipe to reproduce this!

The current behavior of git is that submodule contents aren't updated when the superproject changes. Running "git submodule update" later will then update their content to most submodule changes (but e.g. it won't remove a deleted submodule from the work tree). So yes, this is expected until recursive submodule update materializes (and even then I'm not sure how to handle untracked but not ignored files inside a submodule when stashing will result in the submodule directory to be removed).

Thanks for your responses, all.

Jens: yes, only the index is updated by the stash. The subdirectory
remains and won't be removed (you will actually receive a warning
about `git` not being able to remove it).

I think the core of my misunderstanding is I was used to the idea that when `git status` showed modifications to tracked files, `git stash` would make those modifications disappear. Submodules are fundamentally different, and it makes sense to me now why it wouldn't necessarily be a good idea for `git stash` to be a mutating operation on submodules.

I ran into this behavior while debugging an issue with a git-hook manager I maintain, called Overcommit (https://github.com/brigade/overcommit). It was discovered that if you only add submodule changes to the index and then run `git stash save --keep-index`, an exit status of zero is returned even though no stash was created. I had assumed that if the return code was zero, a stash commit was created, but it makes sense why this is not the case.

Thanks again for your time in helping clarify this behavior.

On Mon, Apr 6, 2015 at 10:58 AM, Jens Lehmann <Jens.Lehmann@web.de> wrote: