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Previews fail via GitHub, work when I retry manually


I have a Hugo blog at GitHub - cariad/unbuild.blog: https://unbuild.blog and a Netlify site to publish it at Netlify App

Up until today, I’ve been able to create pull requests in my blog and have Netlify generate a preview. For example: Add "dinject 1.0.4" by cariad · Pull Request #6 · cariad/unbuild.blog · GitHub

Today, I created a new pull request (Differently 1.0.0 by cariad · Pull Request #7 · cariad/unbuild.blog · GitHub) and Netlify can’t preview it:

2:39:49 PM: Preparing Git Reference pull/7/head
2:39:50 PM: Error fetching branch: https://github.com/cariad/unbuild.blog pull/7/head
2:39:50 PM: Creating deploy upload records
2:39:50 PM: Failing build: Failed to prepare repo
2:39:50 PM: Failed during stage 'preparing repo': exit status 1

However, if I manually clear the cache and retry the same build, it works. The build history is here: Netlify App

I can’t see what I’m doing wrong. Can anybody give me a hand?


Hi @cariad,

The problem is with the Git submodules that you’re using. This is the error we get in our logs:

fatal: remote error: upload-pack: not our ref 050feef06793d1ea675ba99d95c81c5f99bbe5e5
Errors during submodule fetch: themes/tofu-hugo

This is the description of the error: github - Why does git submodule update fail with "fatal: remote error: upload-pack: not our ref"? - Stack Overflow

Thanks @hrishikesh! I’ll look into that now. Do you know why Netlify would be able to pull the submodule when I deploy manually and fail only via the GitHub preview?

Deploy manually? When you deploy manually, Netlify doesn’t pull your repo or build anything.

When I say “manual”, I mean I log into Netflify and click the “clear cache and deploy” button, as opposed to “the preview deploys automatically when I create a pull request.”

Oh, that would be because Netlify cleares the repo and the submodule from cache and fetches it as new. This is what’s executed:

git clone project
cd project
git submodule update -f --init

and this is what’s executed in a cached build:

cd project
git fetch -f -u remote ref
git checkout -f FETCH_HEAD
git submodule update -f --init

If Git throws error in this command, it fails.

Right, thanks! So what I don’t understand it, why does the submodule fail to update when running from a cache?

The submodule’s commit exists. The retry would fail if the commit didn’t exist, right? The retry doesn’t change anything in the repository.

The problem seems to have fixed itself for new pull requests this morning.

I still don’t understand how I could’ve broken the Git submodule as you claim.

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Hi @cariad :wave:

Thanks so much for coming back and confirming that the issue is resolved. Should this issue pop up again in the future, please let us know.

Happy building :netliconfetti: