document target_commitish default (softprops#190)

Author: kevingentile

README.md

@@ -176,7 +176,7 @@ The following are optional as `step.with` keys
 | `tag_name`                 | String  | Name of a tag. defaults to `github.ref`                                                                                                                                                                                                                                                                                                                                                                                                         |
 | `fail_on_unmatched_files`  | Boolean | Indicator of whether to fail if any of the `files` globs match nothing                                                                                                                                                                                                                                                                                                                                                                          |
 | `repository`               | String  | Name of a target repository in `<owner>/<repo>` format. Defaults to GITHUB_REPOSITORY env variable                                                                                                                                                                                                                                                                                                                                              |
-| `target_commitish`         | String  | Commitish value that determines where the Git tag is created from. Can be any branch or commit SHA.                                                                                                                                                                                                                                                                                                                                             |
+| `target_commitish`         | String  | Commitish value that determines where the Git tag is created from. Can be any branch or commit SHA. Defaults to repository default branch.                                                                                                                                                                                                                                                                                                                                             |
 | `token`                    | String  | Secret GitHub Personal Access Token. Defaults to `${{ github.token }}`                                                                                                                                                                                                                                                                                                                                                                          |
 | `discussion_category_name` | String  | If specified, a discussion of the specified category is created and linked to the release. The value must be a category that already exists in the repository. For more information, see ["Managing categories for discussions in your repository."](https://docs.github.com/en/discussions/managing-discussions-for-your-community/managing-categories-for-discussions-in-your-repository)                                                     |
 | `generate_release_notes`   | Boolean | Whether to automatically generate the name and body for this release. If name is specified, the specified name will be used; otherwise, a name will be automatically generated. If body is specified, the body will be pre-pended to the automatically generated notes. See the [GitHub docs for this feature](https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes) for more information |