Allow collect to print to stdout

[gaborbernat]

This would allow tools to collect and visualize the changelogs (in PRs e.g.,) before a release when is hard-coded into the changelog file, via something like https://github.com/oprypin/mkdocs-gen-files.

scriv collect --keep --stdout
# or
scriv print

[kurtmckee]

Hi @nedbat! I am automating my release process across my projects and would like to have exactly this functionality for auto-generating release PR bodies, GitHub releases, and text for the git tags created during releases.

If you're open to this feature, I'm open to implementing it. However, I'd like to know if you have preferences about what the CLI should look like (before I start working on anything).

Both of @gaborbernat's suggestions seem fine with me. The --stdout possibility seems similar to a tee command, and the scriv print possibility would also work.

Looking forward to hearing if you're open to a feature like this!

[nedbat]

scriv print seems like the right way to go.

[nedbat]

This is now released as part of scriv 1.6.0.