docs: describe how to do a release

docs/releasing.md

@@ -0,0 +1,61 @@
+# How to do a release
+
+## Update changelog and Cargo versions
+
+Send a PR similar to https://github.com/jj-vcs/jj/pull/5215. Feel free to
+copy-edit the changelog in order to:
+
+* Populate "Release highlights" if relevant
+* Put more important items first so the reader doesn't miss them
+* Make items consistent when it comes to language and formatting
+
+Producing the list of contributors is a bit annoying. The current suggestion is
+to run something like this:
+
+```shell
+jj log --no-graph -r 'heads(tags())..main' -T 'author ++ "\n"' | sort | uniq -c
+```
+
+Then try to find the right GitHub username for each person and copy their name
+and username from the GitHub page for the person
+(e.g. https://github.com/martinvonz).
+
+Get the PR through review and get it merged as usual.
+
+## Create a tag and a GitHub release
+
+1. Go to https://github.com/jj-vcs/jj/releases and click "Draft a new release"
+2. Click "Choose a tag" and enter "v0.\<number\>.0" (e.g. "v0.26.0") to create a
+   new tag
+3. Click "Target", then "Recent commits", and select the commit from your merged
+   PR
+4. Use the name (e.g. "v0.26.0") as "Release title". Paste the changelog entries
+   into the message body
+5. Check "Create a discussion for this release"
+6. Click "Publish release"
+
+## Publish the crates to crates.io
+
+Go to a terminal and create a new clone of the repo [^1]:
+
+```shell
+cd $(mktemp -d)
+jj git clone https://github.com/jj-vcs/jj
+cd jj
+jj new v0.<number>.0
+```
+
+Publish each crate:
+
+```shell
+(cd lib/proc-macros && cargo publish)
+(cd lib && cargo publish)
+(cd cli && cargo publish)
+```
+
+
+[^1]: We recommend publishing from a new clone because `cargo publish` will
+      archive ignored files if they match the patterns in `[include]`
+      ([example](https://github.com/jj-vcs/jj/blob/b95628c398c6c3d11f41bdf53d0aef11f92ee96d/lib/Cargo.toml#L15-L22)),
+      so it's a security risk to run it an existing clone where you may have
+      left sensitive content in an ignored file.

mkdocs.yml

@@ -132,6 +132,7 @@ nav:
       - 'Code of conduct': 'code-of-conduct.md'
       - 'Design Docs': 'design_docs.md'
       - 'Design Doc Blueprint': 'design_doc_blueprint.md'
+      - 'Releasing': 'releasing.md'
       - 'Temporary Voting for Governance': 'governance/temporary-voting.md'
 
 - 'Design docs':