fix(config): read config from workspace, not git history

[GreenHatHG]

Summary

Fixes #10560

Root Cause

When dvc gc --all-commits traverses commit history, it switches the filesystem to GitFileSystem to read files from git. The Config class then reads configuration files using different filesystems for different levels:

• .dvc/config (repo level): Read from GitFileSystem → gets config from git history
• .dvc/config.local (local level): Read from LocalFileSystem → gets config from workspace

This mixed reading causes incomplete configuration:

• If git history doesn't have the remote url in .dvc/config (e.g., remote was added later or in early commits)
• But workspace has password in .dvc/config.local
• The merged config has password but missing url, causing validation error

The core issue: dvc gc --all-commits --cloud needs the current workspace remote configuration to access cloud storage, but Config class was reading .dvc/config from git history instead of workspace, leading to incomplete or outdated configuration.

Solution

Fixed the mixed reading issue by introducing scenario-aware config loading in Config class:

1. Added _should_prefer_local_dvc_dir property to detect the scenario:

   • Returns True for brancher scenario (dvc gc --all-commits): when dvc_dir is a git root path and workspace has config file.

   • Returns False for Repo(rev="...") scenario: when explicitly accessing a specific revision

2. Updated files property to use consistent source:

   • Brancher scenario: uses local_dvc_dir + wfs for repo config path → reads from workspace
   • Repo(rev="...") scenario: uses dvc_dir + fs for repo config path → reads from git history

3. Updated _get_fs() method to return appropriate filesystem:

   • Brancher scenario: returns wfs for both repo and local levels → unified workspace reading
   • Repo(rev="...") scenario: returns fs for repo level → preserves git history reading

This ensures both .dvc/config and .dvc/config.local are read from the same source, eliminating the mixed reading issue.

Reproduce Bash

mkdir 10560
cd 10560
git init -q
dvc init -q
mkdir data
echo "some test data" > data/file.txt
dvc add data/file.txt
git add .
git commit -m "Add initial data"
dvc remote add -d test-webdav webdav://localhost:9000/
dvc remote modify --local test-webdav password 12345678
dvc gc --all-commits --cloud

error:

ERROR: Failed to collect 'd6fa10d4d819d09f1adb5f4ce244b69fbc2f1ecd': config file error: expected 'url' for dictionary value @ data['remote']['test-webdav']

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.00%. Comparing base (2431ec6) to head (8580c9d).
⚠️ Report is 189 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10965      +/-   ##
==========================================
+ Coverage   90.68%   91.00%   +0.32%     
==========================================
  Files         504      506       +2     
  Lines       39795    41161    +1366     
  Branches     3141     3264     +123     
==========================================
+ Hits        36087    37460    +1373     
- Misses       3042     3063      +21     
+ Partials      666      638      -28     

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[GreenHatHG]

Hi maintainers,

I noticed several unit tests are failing, but they all appear to be unrelated to my changes:

FAILED tests/unit/output/test_load.py::test_load_remote_files_from_pipeline - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/unit/remote/test_remote.py::test_remote_with_hash_jobs - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/unit/remote/test_remote.py::test_remote_with_jobs - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/unit/remote/test_remote.py::test_remote_without_hash_jobs - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/unit/remote/test_remote.py::test_remote_without_hash_jobs_default - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/unit/remote/test_remote.py::test_makedirs_not_create_for_top_level_path[S3FileSystem] - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/unit/stage/test_loader_pipeline_file.py::test_fill_from_lock_use_appropriate_checksum - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/unit/stage/test_serialize_pipeline_lock.py::test_dump_nondefault_hash - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/func/test_dataset.py::test_url - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies
FAILED tests/func/test_dataset.py::test_url_dataset_pipeline - dvc_objects.fs.errors.RemoteMissingDepsError: filesystem for 's3': '<class 'dvc_s3.S3FileSystem'>' missing dependencies

[GreenHatHG]

Hi maintainers,
In the previous version, dvc/config.py had some missing and partial line coverage. I have added the necessary test cases in the latest commit.
Ready for review when you have a moment. Thanks!