Post: deprecate old VCS support (#264)

* Post: deprecate old VCS support

Blog post to communicate our users about the deprecation of old VCS support:

- clear date on final removal
- clear brownout dates
- possible workarounds

Related readthedocs/readthedocs.org#8840

* Bold dates

* Apply suggestions from code review

Co-authored-by: Anthony <[email protected]>

* Minor updates

* Add "product complexity" as reason for deprecation

* Add image

* Update content/posts/drop-support-for-subversion-mercurial-bazaar.md

Co-authored-by: Anthony <[email protected]>

* Updates from review

* Apply suggestions from code review

Co-authored-by: Eric Holscher <[email protected]>

* Apply suggestions from code review

---------

Co-authored-by: Anthony <[email protected]>
Co-authored-by: Eric Holscher <[email protected]>

Author: 3 people

content/images/drop-support-for-subversion-mercurial-bazaar.jpg

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+title: Dropping support for Subversion, Mercurial, and Bazaar
+date: 2024-02-22
+category: Changelog
+tags: builders, deprecation
+authors: Manuel Kaufmann
+status: published
+image: /images/drop-support-for-subversion-mercurial-bazaar.jpg
+image_credit: Photo by <a href="https://unsplash.com/@redmirror?utm_content=creditCopyText&utm_medium=referral&utm_source=unsplash">Red Mirror</a> on <a href="https://unsplash.com/photos/wall-with-paints-f303VzauP6w?utm_content=creditCopyText&utm_medium=referral&utm_source=unsplash">Unsplash</a>
+
+
+We are announcing the deprecation of support for Bazaar, Mercurial, and Subversion version control systems starting on **Monday, June 3rd, 2024**.
+After this date, only Git repositories will be continue to be supported by our application.
+
+We've made this hard decision because [99% of our projects](https://github.com/readthedocs/readthedocs.org/issues/8840) use Git
+and we can't cover the product complexity, documentation complexity, and maintenance cost we were spending on Bazaar, Mercurial and Subversion for a small number of projects.
+Our platform has long had fewer features for VCS systems other than Git,
+slowly adding confusion to our product,
+and slowing down the features we could build for the vast majority of our users on Git.
+
+## Deprecation timeline
+
+We understand this change will affect some of our users, so we have a timeline to communicate this deprecation to our users effectively.
+
+* **Monday, April 1, 2024**: Do the first brownout (temporarily enforce this deprecation) for 12 hours: 00:01 PDT to 11:59 PDT (noon)
+* **Monday, May 6, 2024**: Do a second brownout (temporarily enforce this deprecation) for 24 hours: 00:01 PDT to 23:59 PDT (midnight)
+* **Monday, May 20, 2024**: Do a third and final brownout (temporarily enforce this deprecation) for 48 hours: 00:01 PDT to May 21, 2024 23:59 PDT (midnight)
+* **Monday, June 3, 2024**: Fully remove support for building documentation using Subversion, Mercurial or Bazaar VCSs.
+
+
+## Possible workarounds
+
+To continue building your project, you could consider one of the following options:
+
+
+### Convert your repository to Git
+
+You could convert your Subversion or Mercurial repository to Git and then connect the Git repository to your project to continue building your docs.
+GitHub has some guides to help you in this process:
+
+  * [Import your Subversion repository](https://docs.github.com/en/migrations/importing-source-code/using-the-command-line-to-import-source-code/importing-a-subversion-repository)
+  * [Import your Mercurial repository](https://docs.github.com/en/migrations/importing-source-code/using-the-command-line-to-import-source-code/importing-a-mercurial-repository)
+
+
+### Create an intermediate Git repository only for initial clone
+
+
+If you cannot use Git for your documentation repository,
+an intermediate Git repository could at least allow your project to build.
+Understand however that this is not a supported configuration and
+many of our features may not work (e.g. versions) or might require extra setup steps.
+
+This intermediate repository should contain a `.readthedocs.yaml` file
+that clones your original repository and builds your project's documentation.
+
+Here you have a small example using Mercurial to clone the original repository.
+*Make sure to adapt this example to your needs*
+
+```yaml
+version: 2
+
+build:
+  os: ubuntu-22.04
+  tools:
+    python: "3.12"
+  jobs:
+    post_checkout:
+      - hg clone https://original.mercurial.vcs/respository/ .
+
+sphinx:
+  configuration: docs/conf.py
+```
+
+This could be a starting point, but note that you will also need to configure the incoming webhooks manually on the original repository,
+if you want to trigger a build each time a push is done to the original repository.
+[Follow this guide](https://docs.readthedocs.io/en/stable/guides/setup/git-repo-manual.html) to achieve this.
+
+
+## Contact us
+
+[Contact us](https://readthedocs.org/support/) if you have any questions,
+and let us know any inconvenient you may have with this change.