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

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

@@ -0,0 +1,72 @@
+title: Drop support for Subversion, Mercurial and Bazaar
+date: 2024-02-19
+category: Changelog
+tags: builders, deprecation
+authors: Manuel Kaufmann
+status: published
+
+
+We are announcing the dropping of support for Bazaar, Mercurial and Subversion version system controls starting on **Monday, June 3rd, 2024**.
+This means we will only support Git to do the initial clone and build your project's documentation.
+
+We've made this hard decision because [99% of our users](https://github.com/readthedocs/readthedocs.org/issues/8840) use Git
+and we can't cover the maintenance cost we were spending on Bazaar, Mercurial and Subversion for a handful amount of projects.
+Besides, those VCSs are not feature-complete in our platform compared to Git and the service provided is degraded for them.
+
+## 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 PST to 11:59 PST (noon)
+* Monday, May 6, 2024: Do a second brownout (temporarily enforce this deprecation) for 24 hours: 00:01 PST to 23:59 PST (midnight)
+* Monday, May 20, 2024: Do a third and final brownout (temporarily enforce this deprecation) for 48 hours: 00:01 PST to May 21, 2024 23:59 PST (midnight)
+* Monday, June 3, 2024: Fully remove support for building documentation using “build.image” on the configuration file
+
+
+## Possible workarounds
+
+Unfortunately, there is no direct workaround on the Read the Docs side that you can follow to keep building your documentation using these VCSs.
+However, we consider one of the following options can be worth to consider:
+
+
+### Convert your repository to Git
+
+You could convert your Subversion or Mercurial repository to Git and then import the Git repository into Read the Docs 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 a simple Git repository only clone the original one
+
+If you want to keep using Bazaar, Mercurial or Subversion on your side,
+you can create a simple Git repository on any service only with a simple `.readthedocs.yaml` file
+that clones your original repository to build the docs.
+
+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"
+  commands:
+    - hg clone https://original.mercurial.vcs/respository/
+    - pip install -r repository/docs/requirements.txt
+    - mkdir $READTHEDOCS_OUTPUT/html
+    - sphinx-build -b html repository/docs $READTHEDOCS_OUTPUT/html
+```
+
+This could be a good 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 if you are having trouble using a this new config key for any reason.