fix(check): expand env vars in --rev-range

[bearomorphism]

Description

Fix regression where the packaged commitizen-branch pre-push hook stopped working after v4.15.0.

The hook passes the literal .. as a single argv element. Before #1941 the surrounding shell=True expanded the env vars; after #1941 (CWE-78 hardening) git receives the literal string and aborts with fatal: ambiguous argument.

Fix: expand env vars on the --rev-range argument via os.path.expandvars in Check.__init__. Unset vars are left literal so git can surface a clear error rather than silently rewriting the range to empty.

Closes #2003. Credit to @j178 for the root-cause analysis.

Checklist

• I have read the contributing guidelines

Was generative AI tooling used to co-author this PR?

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Generated-by: GitHub Copilot CLI following the guidelines

Code Changes

• Add test cases to all the changes you introduce
• Run uv run poe all locally to ensure this change passes linter check and tests
• Manually test the changes
• Update the documentation for the changes (N/A -- no user-facing CLI change)

Expected Behavior

cz check --rev-range "$VAR1..$VAR2" resolves env vars before invoking git log, matching the pre-#1941 contract that the packaged hook relied on.

Steps to Test This Pull Request

git init repro && cd repro
git commit --allow-empty -m "feat: first"
git commit --allow-empty -m "fix: second"
export PRE_COMMIT_FROM_REF=$(git rev-parse HEAD~1)
export PRE_COMMIT_TO_REF=$(git rev-parse HEAD)
cz check --rev-range "$PRE_COMMIT_FROM_REF..$PRE_COMMIT_TO_REF"

Before: fatal: ambiguous argument (exit 23). After: Commit validation: successful!.

New automated coverage in tests/commands/test_check_command.py: two unit tests plus test_check_rev_range_pre_commit_branch_hook_regression -- an E2E test against a real git repo that reproduces the exact issue error when the fix is reverted.

[github-actions]

🔍 Commitizen bump preview

Merging this PR will produce the following bump:

bump: version 4.16.2 → 4.16.3
tag to create: v4.16.3
increment detected: PATCH

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.24%. Comparing base (c3f6797) to head (2a3213e).
⚠️ Report is 3 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2005   +/-   ##
=======================================
  Coverage   98.24%   98.24%           
=======================================
  Files          61       61           
  Lines        2785     2787    +2     
=======================================
+ Hits         2736     2738    +2     
  Misses         49       49           

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[Copilot]

Pull request overview

This PR fixes the cz check --rev-range path used by the packaged commitizen-branch pre-push hook by expanding environment variables in the revision range before invoking git, preserving the pre-shell=False behavior without reintroducing shell execution.

Changes:

• Adds os.path.expandvars handling for Check.rev_range.
• Adds unit coverage for expanded and unset environment variables.
• Adds an end-to-end regression test using a real git repo for the pre-push hook scenario.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
commitizen/commands/check.py	Expands environment variables in --rev-range before git commit lookup.
tests/commands/test_check_command.py	Adds regression coverage for env-var expansion and the packaged pre-push hook flow.

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[bearomorphism]

The new tests will fail without the code change in check.py. Now it's ready for review.