Adds a signoff_commit configuration option so that automated version-bump commits can include a Signed-off-by trailer, supporting Developer Certificate of Origin (DCO) compliance for release automation.

Configuration

• Added signoff_commit: bool (default False) to RawConfig and RuntimeContext in src/semantic_release/cli/config.py, following the same pattern as no_git_verify.

Git commit logic

• Added a signoff parameter to GitProject.git_commit() in src/semantic_release/gitproject.py. Since this method already shells out to the real git commit binary (via repo.git.commit(...)), signoff is implemented by passing signoff=True through to git's native --signoff flag rather than manually constructing the trailer — git generates the correct Signed-off-by: Name <email> line using the already-configured committer identity.
• Noop output now reflects --signoff when the option is enabled.

Wiring

• cli/commands/version.py reads runtime.signoff_commit and passes it to project.git_commit(...) when creating the version commit.

Documentation

• Documented signoff_commit in docs/configuration/configuration.rst.

Example config:

[tool.semantic_release]
signoff_commit = true

Resulting commit message:

chore(release): bump version to 1.2.3

Signed-off-by: semantic-release <semantic-release@example.com>

Closes: #1441