site: devguide: note new changelog/relnotes process

site/contributing.md

@@ -741,6 +741,32 @@ Project documentation lives in a number of places:
 - `doc/notes.org` has some old developer notes
 - developer reports (profiles, benchmarks, coverage..) in doc/profs, sometimes published at hledger.org/profs
 
+How to prepare changelogs & release notes
+
+Draft:
+
+- `make changelog-draft >> doc/CHANGES.draft.org` (or `>` if this is the first draft)
+- open this org file and sort the nodes (`C-c ^ a`)
+- categorisation pass 1: go through and add topic prefixes where missing
+- sort the nodes again
+- categorisation pass 2: move significant items to the appropriate package subnode as appropriate; keep "soft" items that might appear in release notes; delete the rest
+- cleanup pass: combine/rewrite items for clarity
+
+Changelogs:
+
+- choose release version and date
+- add new sections at top of {doc,hledger*}/CHANGES
+- move the items from CHANGES.draft.org to these CHANGES files
+- remove CHANGES.draft.org
+
+Release notes:
+
+- add a new TOC entry and section in site/release-notes.md
+- copy/rewrite/summarise package changelogs 
+- note any other items of interest
+- list release contributors
+- write release summary
+
 ### Code
 
 hledger is a suite of applications, tools and libraries.