Remove broken client.branch.diff_data()

[saltas888]

Why

client.branch.diff_data() has never worked: it calls GET /api/diff/data, an endpoint removed from Infrahub in opsmill/infrahub#4865, and its URL builder is also missing the ? separator, so every call returns a 404 (#325).

opsmill/infrahub#8594 tried to fix this by adding the missing REST endpoint back, but as @ogenstad pointed out there, the SDK should use existing queries/mutations rather than get a server endpoint of its own, and the broken method should be removed or refactored instead.

The SDK already has GraphQL-based diff methods (get_diff_tree(), get_diff_summary(), both backed by the DiffTree query), but they only fetched summary counts, while the original diff_data() returned the data-level diff including previous/new values. So this PR removes the broken method and extends get_diff_tree() to cover what diff_data() was meant to provide.

Closes #325

What changed

• Removed diff_data() from InfrahubBranchManager and InfrahubBranchManagerSync
• Removed InfraHubBranchManagerBase, whose only content was the diff_data URL builder (generate_diff_data_url)
• Added include_properties to client.get_diff_tree() (async and sync), when True the diff tree includes value-level details per change: previous/new value per attribute property, and peer id/label per relationship element
• Rewrote the "Generating a diff for a branch" section of the branches guide to use client.get_diff_tree() / client.get_diff_summary()
• Changelog entries (removed + added)

Since the method has returned a 404 for as long as the endpoint has been absent, no working code can be calling it, removal without a deprecation cycle should be safe.

How to review

1. infrahub_sdk/branch.py, pure deletion
2. infrahub_sdk/diff.py, the include_properties extension of the query builder and response parsing
3. tests/integration/test_diff_tree.py, end-to-end coverage against a live Infrahub (attribute value change + relationship peer change)
4. docs/docs/python-sdk/guides/branches.mdx, the replacement guidance

How to test

uv run pytest tests/unit/sdk/test_diff_summary.py
uv run pytest tests/integration/test_diff_tree.py

Impact & rollout

• Backward compatibility: removes a public method that could not be used successfully; callers migrating should switch to get_diff_tree() / get_diff_summary() (note there is no branch_only equivalent, DiffTree always compares the branch against its base). include_properties defaults to False, existing get_diff_tree() callers are unaffected.
• Config/env changes: none

Checklist

• Tests added/updated
• Changelog entry added
• External docs updated
• Internal .md docs updated (n/a)

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[codecov]

Codecov Report

❌ Patch coverage is 97.91667% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
infrahub_sdk/diff.py	97.67%	0 Missing and 1 partial ⚠️

@@                 Coverage Diff                  @@
##           infrahub-develop    #1229      +/-   ##
====================================================
+ Coverage             84.00%   84.13%   +0.12%     
====================================================
  Files                   147      147              
  Lines                 13063    13078      +15     
  Branches               1932     1936       +4     
====================================================
+ Hits                  10974    11003      +29     
+ Misses                 1522     1507      -15     
- Partials                567      568       +1     

Flag	Coverage Δ
integration-tests	39.28% <50.00%> (+0.32%)	⬆️
python-3.10	56.95% <56.25%> (+0.11%)	⬆️
python-3.11	56.95% <56.25%> (+0.10%)	⬆️
python-3.12	56.94% <56.25%> (+0.10%)	⬆️
python-3.13	56.95% <56.25%> (+0.11%)	⬆️
python-3.14	56.94% <56.25%> (+0.08%)	⬆️
python-filler-3.12	23.64% <41.66%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
infrahub_sdk/branch.py	82.11% <100.00%> (+7.63%)	⬆️
infrahub_sdk/client.py	79.76% <100.00%> (ø)
infrahub_sdk/diff.py	96.77% <97.67%> (+0.34%)	⬆️

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All reported issues were addressed across 8 files (changes from recent commits).

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