docs: document release process steps

Author: MightyCreak

docs/release-process.md

@@ -0,0 +1,56 @@
+# Release process
+
+I'd wish the release process to be more automated, but for now it's still a
+few manual steps.
+
+## Prepare the PR for the new release
+
+1. Find the next version, using semantic versioning, depending on the changes
+   in the changelog
+2. Find and replace the old version with the new version in some files:
+   - meson.build
+   - data/usr/share/gnome/help/diffuse/*/diffuse.xml
+   - data/usr/share/omf/diffuse/diffuse-*.omf
+   - utils/book2manual.xsl
+   - windows-installer/build.py
+   - windows-installer/diffuse.iss
+   - windows-installer/diffuse.new.iss
+3. Update the date for the new release date in these files:
+   - data/usr/share/gnome/help/diffuse/*/diffuse.xml
+   - data/usr/share/omf/diffuse/diffuse-*.omf
+   - utils/book2manual.xsl
+3. Update CHANGELOG.md
+   - Add new line under `## Unreleased` following this syntax: `## x.y.z - YYYY-MM-DD`
+   - Copy the content of the changes for this release
+4. Update AppData release notes in data/io.github.mightycreak.Diffuse.appdata.xml.in:
+   - Create a new `<release>` tag under `<releases>`, fill the `version` and
+     `date` attributes
+   - Create a new `<description>` tag under the new `<release>` tag
+   - Add one paragraph to sum the release in one sentence (e.g. highlights, ...)
+   - Paste the changes from the changelog and adapt it to HTML
+5. Create new branch and PR
+
+## Create new release on GitHub
+
+1. When everything's green: merge the PR
+2. Create a new release on GitHub's [new release page](https://github.com/MightyCreak/diffuse/releases/new):
+   - Choose a tag: `v` followed with the new version (e.g. `v1.2.3`)
+   - Release title: the tag (e.g. `v1.2.3`)
+   - Description:
+     - For the first paragraph, paste the first paragraph from the release notes
+     - For the second paragraph, got to [CHANGELOG.md](https://github.com/MightyCreak/diffuse/blob/master/CHANGELOG.md)
+       and copy the URL anchor to the new release, then add this sentence
+       (adapt the changelog link):  
+       > For a more detailed list of changes, see the
+       > [changelog](https://github.com/MightyCreak/diffuse/blob/master/CHANGELOG.md#xyz---yyyy-mm-dd).
+3. Publish release
+
+## Create new release on Flatpak
+
+1. Clone the Flathub repository: https://github.com/flathub/io.github.mightycreak.Diffuse
+2. Copy the contents of Diffuse's `io.github.mightycreak.Diffuse.yml` to Flathub's
+3. Keep Flathub's `config-opts` and `sources` sections
+4. In `sources` section, change the `commit` and `tag`
+5. Create commit with changes and push to `master`
+6. Check the build on Flathub: https://flathub.org/builds/
+7. When it's done and successful, publish the build