release: Add release instructions and script

Stolen from wayland and weston. Adjusted slightly to fit our needs.

Signed-off-by: Sebastian Wick <sebastian.wick@redhat.com>

release.sh

@@ -0,0 +1,80 @@
+#!/bin/sh -eu
+
+build_dir=build-release
+
+if ! type glab >/dev/null; then
+	echo "glab is needed to create a release"
+	exit 1
+fi
+
+case "$(git rev-parse --abbrev-ref HEAD)" in
+main | [0-9]*.[0-9]*)
+	;;
+*)
+	echo "Not on the main or a stable branch"
+	exit 1
+esac
+
+if [ -n "$(git log @{upstream}..)" ]; then
+	echo "The main branch has unpushed commits"
+	exit 1
+fi
+
+meson_options=""
+if [ -e "$build_dir" ]; then
+	meson_options="$meson_options --wipe"
+fi
+meson setup "$build_dir" $meson_options
+
+prev_version="$(git describe --tags --abbrev=0 || git rev-list --max-parents=0 --first-parent HEAD)"
+version="$(meson introspect "$build_dir" --projectinfo | jq -r .version)"
+if [ "$version" = "$prev_version" ]; then
+	echo "Version not bumped"
+	exit 1
+fi
+
+name="$(meson introspect "$build_dir" --projectinfo | jq -r .descriptive_name)"
+if [ "$name" = "" ]; then
+	echo "Cannot determine project name"
+	exit 1
+fi
+
+ninja -C "$build_dir" dist
+
+archive_name="$name-$version.tar.xz"
+archive_path="$build_dir/meson-dist/$archive_name"
+gpg --detach-sig "$archive_path"
+
+sha256="$(cd $build_dir/meson-dist && sha256sum $archive_name)"
+sha512="$(cd $build_dir/meson-dist && sha512sum $archive_name)"
+archive_url="https://gitlab.freedesktop.org/emersion/$name/-/releases/$version/downloads/$archive_name"
+announce_path="$build_dir/meson-dist/$name-$version-announce.eml"
+current_branch=$(git branch --show-current)
+remote_name=$(git config --get branch.${current_branch}.remote)
+
+cat >"$announce_path" <<EOF
+To: <wayland-devel@lists.freedesktop.org>
+Subject: [ANNOUNCE] $name $version
+
+`git shortlog --no-merges "$prev_version.."`
+
+git tag: $version
+
+$archive_url
+SHA256: $sha256
+SHA512: $sha512
+PGP:    $archive_url.sig
+EOF
+
+echo "Release announcement written to $announce_path"
+
+echo -n "Release $name $version? [y/N] "
+read answer
+if [ "$answer" != "y" ]; then
+	exit 1
+fi
+
+git tag -s -m "$version" "$version"
+git push "$remote_name" "$version"
+glab release create "$version" "$archive_path"* --notes ""
+

releasing.md

@@ -0,0 +1,41 @@
+# Releasing
+
+To make a release of libdisplay-info, follow these steps.
+
+0. Verify the test suites and codebase checks pass.  All of the tests should
+   either pass or skip.
+
+       ninja -C build/ test
+
+1. Update the first stanza of `meson.build` to the intended version.
+
+   Then commit your changes:
+
+       RELEASE_NUMBER="x.y.z"
+       RELEASE_NAME="[alpha|beta|RC1|RC2|official|point]"
+       git status
+       git commit meson.build -m "build: bump to version $RELEASE_NUMBER for the $RELEASE_NAME release"
+       git push
+
+2. Run the `release.sh` script to generate the tarballs, sign and upload them,
+   and generate a release announcement template.
+
+3. Compose the release announcements.  The script will generate a
+   libdisplay-info-x.y.z.announce file with a list of changes and tags.  Prepend
+   these with a human-readable listing of the most notable changes.  For x.y.0
+   releases, indicate the schedule for the x.y+1.0 release.
+
+4. PGP sign the release announcement and send it to
+   <wayland-devel@lists.freedesktop.org>.
+
+For x.y.0 releases, also create the release series x.y branch.  The x.y branch
+is for bug fixes and conservative changes to the x.y.0 release, and is where we
+create x.y.z releases from.  Creating the x.y branch opens up main for new
+development and lets new development move on.
+
+    git branch x.y [sha]
+    git push origin x.y
+
+For stable branches, we commit fixes to main first, then `git cherry-pick -x`
+them back to the stable branch.
+