git prevents pulling upstream due to non-existent local changes

[GuMiner]

• I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?

64-bit. However, this also repros on the macOS build of Git.

$ git --version --build-options
git version 2.34.0.vfs.0.0
cpu: x86_64
built from commit: 599a56ae91cee374b95d19c73aeead6ea18ea7a2
sizeof-long: 4
sizeof-size_t: 8
shell-path: /bin/sh
feature: fsmonitor--daemon

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver
Microsoft Windows [Version 10.0.19044.1348]

• What options did you set as part of the installation? Or did you choose the
  defaults?

# One of the following:
> type "C:\Program Files\Git\etc\install-options.txt"
Editor Option: VIM
Custom Editor Path:
Default Branch Option:
Path Option: Cmd
SSH Option: OpenSSH
Tortoise Option: false
CURL Option: OpenSSL
CRLF Option: CRLFAlways
Bash Terminal Option: MinTTY
Git Pull Behavior Option: Merge
Use Credential Manager: Core
Performance Tweaks FSCache: Enabled
Enable Symlinks: Disabled
Enable Pseudo Console Support: Disabled
Enable FSMonitor: Disabled

• Any other interesting things about your environment that might be related
  to the issue you're seeing?

I already had a sparse-checkout repository before using this version of Git.

Details

• Which terminal/shell are you running Git from? e.g Bash/CMD/PowerShell/other

Bash

• What commands did you run to trigger this issue? If you can provide a
  Minimal, Complete, and Verifiable example
  this will help us understand the issue.

git pull origin <my-branch>

Unfortunately, this issue happened after using this version of git for a while and continued until I added the affected file paths to my sparse checkout list.

• What did you expect to occur after running these commands?

Git pulls from the upstream

• What actually happened instead?

Git didn't pull because files were changed that didn't exist locally. These file paths were not in my sparse checkout list. For instance, devapk/excel/en-us existed in the sparse-checkout list, but not devapk/excel/ja-jp.pseudo

git pull origin <my-branch>
Prefetch 1638298835 (2021-11-30 19:00:35 +0000) (bytes received): 8, done.
From https://dev.azure.com/office/office/_git/Office
 * branch                      official/appleauto -> FETCH_HEAD
warning: Fetch normally indicates which branches had a forced update,
but that check has been disabled. To re-enable, use '--show-forced-updates'
flag or run 'git config fetch.showForcedUpdates true'.
error: Your local changes to the following files would be overwritten by merge:
        devapk/excel/ja-jp.pseudo/product/build.gradle
        devapk/excel/ja-jp.pseudo/product/sources
        devapk/officemobile/ja-jp.pseudo/product/build.gradle
        devapk/officemobile/ja-jp.pseudo/product/sources
        devapk/onenote/ja-jp.pseudo/product/modernonenote/apk/build.gradle
        devapk/onenote/ja-jp.pseudo/product/modernonenote/apk/sources
        devapk/ppt/ja-jp.pseudo/product/build.gradle
        devapk/ppt/ja-jp.pseudo/product/sources
        devapk/rio/ar-sa.pseudo/build.gradle
        devapk/word/ja-jp.pseudo/product/build.gradle
        devapk/word/ja-jp.pseudo/product/sources
Please commit your changes or stash them before you merge.
Aborting
Updating 608889a9daba..bac8a2bed9c1
Calling 'git fetch' to pick up upstream refs...
Prefetch 1638298835 (2021-11-30 19:00:35 +0000) (bytes received): 8, done.
warning: Fetch normally indicates which branches had a forced update,
but that check has been disabled. To re-enable, use '--show-forced-updates'
flag or run 'git config fetch.showForcedUpdates true'.

• If the problem was occurring with a specific repository, can you provide the
  URL to that repository to help us with testing?

https://office.visualstudio.com/Office/_git/Office

[GuMiner]

See also: This Teams thread:
https://teams.microsoft.com/l/message/19:[email protected]/1638314586080?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=fe22c40d-26d1-4326-9e03-56f31dfcbc63&parentMessageId=1638314586080&teamName=Office%20Git%2FAzure%20DevOps%20Transition&channelName=Help%20Me!&createdTime=1638314586080

[derrickstolee]

Thanks for the report, @GuMiner. Do you still have a repro?

My guess is that you had some files leftover from a previous change that were left by a previous Git version, and git sparse-checkout reapply would have fixed this for you, too.

I have added these instructions to the release notes:

🚨 Special Instructions 🚨

If this is your first time using the sparse index, then you will need to run the following command after installing:

git sparse-checkout reapply

If we do get a repro of this issue, then the following would help us diagnose the problem:

1. Run scalar diagnose and note where it places a .zip file. (It is important that you do this before adjusting the sparse-checkout.)
2. Does the same thing happen if you run git fetch origin <branch> followed by git merge origin/<branch>?
3. Does it happen again after running git sparse-checkout reapply?

Finally, sending the .zip from the scalar diagnose command to [email protected] would allows us to examine your index and related ref state to try and create a reproduction.

[GuMiner]

Unfortunately I no longer have a repro. However, I can confirm I did not run git sparse-checkout reapply after installing the new Git version.

[derrickstolee]

Thanks to Mike Marcelais, we found a reproducible situation that allowed us to tackle and fix this problem. The pull request is available as #473. We intend to review, merge, and release that fix early next week. (We will discuss as a team whether we should include other fixes, such as merging 2.34.1 or #470.)