doc: add release_process.md

doc/release_process.md

@@ -0,0 +1,10 @@
+# Release Process
+
+1. Open PR that
+   1. adds release notes to `doc/CHANGELOG.md` and
+   2. updates `_PKG_VERSION_{MAJOR,MINOR,BUILD}` and `_LIB_VERSIONS_*` in `configure.ac`
+2. After merge, create a release branch with name `MAJOR.MINOR.PATCH`. Make sure that the branch contains the right commits.
+3. Create commit on the release branch that sets `_PKG_VERSION_IS_RELEASE` in `configure.ac` to `true`.
+4. Tag the commit with `git tag -s vMAJOR.MINOR.PATCH`.
+5. Push branch and tag with `git push origin --tags`.
+6. Create a new GitHub release with a link to the corresponding entry in `doc/CHANGELOG.md`.