fix(security): prevent command injection via shell=True (CWE-78)

[bearomorphism]

Description

Fix command injection vulnerability (CWE-78) where shell=True in cmd.run() allowed arbitrary command execution via user-controlled values interpolated into git commands (e.g., annotated_tag_message in pyproject.toml).

Closes #1918

Changes

Split cmd.run() into two explicit APIs:

• cmd.run(Sequence[str]) -- executes commands with shell=False (safe, no injection)
• cmd.run(str) -- deprecated, emits DeprecationWarning, still uses shell=True for backward compat
• cmd.run_shell(str) -- explicit opt-in for shell=True (only used by user-defined hooks)

Converted all git operations to list-based execution (shell=False):

• git.tag(), git.add(), git.commit(), git.get_commits(), git.get_tags()
• git.get_filenames_in_commit(), git.tag_exist(), git.is_signed_tag()
• git.get_tag_message(), git.get_tag_names(), git.find_git_project_root()
• git.is_staging_clean(), git.is_git_project(), git.get_core_editor()
• git._get_log_as_str_list(), git.get_default_branch()

Eliminated args string splitting (list->string->list round-trip):

• git.commit(args=...) and git.get_commits(args=...) now accept Sequence[str] instead of str
• cli.py passes extra_cli_args as a list directly from argparse (no " ".join())
• bump._get_commit_args() returns list[str] instead of joined string
• This preserves arguments with spaces that were previously broken by naive .split()

Other improvements:

• git.commit() uses env={"GIT_COMMITTER_DATE": ...} instead of OS-specific shell tricks (cmd /v /c on Windows, env prefix on Unix)
• Removed _create_commit_cmd_string() helper (no longer needed)
• Removed shell quoting artifacts from get_tags() and get_tag_message() format strings (fixes a Windows bug where literal quotes appeared in output)
• hooks.py uses cmd.run_shell() -- intentionally shell-based for user-defined hooks with pipes/redirects

Checklist

• I have read the contributing guidelines

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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:
  • Verify the feature/bug fix works as expected in real-world scenarios
  • Test edge cases and error conditions
  • Ensure backward compatibility is maintained
  • Document any manual testing steps performed
• Update the documentation for the changes

Documentation Changes

N/A - Internal implementation change only, no user-facing behavior or CLI changes.

Expected Behavior

User-controlled values (tag names, messages, file paths) are passed as literal arguments to git commands without shell interpretation, preventing command injection attacks in CI/CD pipelines.

Steps to Test This Pull Request

1. Create a pyproject.toml with a malicious annotated_tag_message:

   [tool.commitizen]
   name = "cz_conventional_commits"
   version = "0.1.0"
   tag_format = "$version"
   annotated_tag = true
   annotated_tag_message = 'Release" && echo INJECTED && echo "'

2. Run cz bump --yes
3. Verify that INJECTED is NOT printed (command not executed)
4. Verify the tag is created with the literal message string

Verification: All Attack Vectors from #1918 Addressed

Affected code (from issue)	Fix applied
cmd.run(f'git tag {option} {tag} -m "{msg or tag}"')	cmd.run(["git", "tag", option, tag, "-m", msg or tag]) (line 177)
cmd.run(f"git tag {tag}")	cmd.run(["git", "tag", tag]) (line 171)
cmd.run(f"git add {' '.join(args)}")	cmd.run(["git", "add", *args]) (line 181)
subprocess.Popen(cmd, shell=True)	shell=False for all list-based cmd.run() calls

Manual validation result: Running cz bump with a malicious annotated_tag_message = 'Release" && echo INJECTED && echo "' -- the injected command was NOT executed, and the tag was created with the literal string as its message.

Backward Compatibility

cmd.run() accepts both str (deprecated, emits DeprecationWarning, uses shell=True) and Sequence[str] (safe, shell=False). External plugins calling cmd.run("git ...") will continue to work but receive a deprecation warning guiding them to migrate.

Additional Context

Related: CWE-78 (OS Command Injection)

The attack vector requires a poisoned pyproject.toml (e.g., via malicious PR) that gets executed in CI/CD running cz bump. With shell=True, values like annotated_tag_message were interpolated into shell command strings, allowing arbitrary command execution. With shell=False + list args, each value is a literal argv entry -- shell metacharacters (&&, ;, |, backticks) have no special meaning.

[codecov]

Codecov Report

❌ Patch coverage is 98.50746% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 98.23%. Comparing base (b4f4209) to head (90b055b).
⚠️ Report is 3 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
commitizen/commands/init.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1941      +/-   ##
==========================================
+ Coverage   98.10%   98.23%   +0.12%     
==========================================
  Files          61       61              
  Lines        2748     2772      +24     
==========================================
+ Hits         2696     2723      +27     
+ Misses         52       49       -3     

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[Copilot]

Pull request overview

This PR hardens command execution throughout Commitizen by separating safe subprocess usage from explicit shell execution, addressing the reported shell=True command-injection path in git operations and related CLI argument handling.

Changes:

• Split command execution into cmd.run() for argv-based safe execution and cmd.run_shell() for intentional shell use in hooks.
• Converted git-related commands and commit/changelog argument plumbing from shell strings to list-based subprocess arguments.
• Updated tests to cover the new command APIs, env passing, hook execution, and list-based CLI/git argument handling.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/utils.py	Updates test helpers to use argv-based git commands and trims branch-name output.
tests/test_git.py	Revises git tests for list-based command execution and new commit/env behavior.
tests/test_conf.py	Switches test repo setup to argv-based git init.
tests/test_cmd.py	Adds direct tests for cmd.run, cmd.run_shell, and env propagation.
tests/test_bump_hooks.py	Updates hook tests to patch run_shell and adds integration coverage.
tests/test_bump_create_commit_message.py	Replaces shell-string git commands in bump/changelog tests and keeps hook install via shell.
tests/conftest.py	Converts fixture setup and GPG/git config helpers to argv-based commands.
tests/commands/test_commit_command.py	Updates commit-command expectations to list args and adds CLI extra-args parsing coverage.
tests/commands/test_bump_command.py	Adjusts git command assertions and replaces shell filesystem setup with Path APIs.
commitizen/hooks.py	Routes user-defined hooks through explicit run_shell().
commitizen/git.py	Converts git operations to safe argv execution, passes commit env explicitly, and removes shell-string commit construction.
commitizen/commands/init.py	Builds pre-commit install as argv instead of a shell string.
commitizen/commands/commit.py	Changes extra git args from string to list[str] and forwards them directly to git.commit().
commitizen/commands/changelog.py	Passes topo-order git-log args as a list.
commitizen/commands/bump.py	Returns commit args as list[str] for safe downstream execution.
commitizen/cmd.py	Introduces shared _popen() plus explicit safe run() and shell-based run_shell() APIs.
commitizen/cli.py	Preserves extra CLI args as a list instead of joining/splitting a string.

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