changelog: get unreleased entries from commit trailers

Asking contributors to update the CHANGELOG.md file is causing lots of
merge conflicts. Introduce a new workflow where contributors can attach
changelog entries in patches via git trailers.

Changelog-added: For new features.
Changelog-fixed: For bug fixes.
Changelog-changed: For behaviour or config format changes.
Changelog-deprecated: For deprecation or removal of functionality.

If a complete trailer is longer than 72 characters, it can be continued
by indenting extra lines with a single space. The trailer text must be
valid markdown.

Update CONTRIBUTING.md with new guidelines.

Update contrib/release.sh to extract these trailers before tagging and
create a new section in CHANGELOG.md.

Extract unreleased entries in this commit to follow the new workflow.

Changelog-added: New `flagged` criteria for `:sort`.
Changelog-added: New `:send-keys` command to control embedded terminals.
Changelog-added: Account aliases now support fnmatch-style wildcards.
Changelog-fixed: `colorize` support for wildcards `?` and `*`.
Signed-off-by: Robin Jarry <robin@jarry.cc>
Acked-by: Moritz Poldrack <moritz@poldrack.dev>

4 files changed, 33 insertions, 17 deletions

diff --git a/.gitignore b/.gitignore
index 2ce89f33..9d9a732e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,5 @@
 *.1
 *.5
 *.7
+/.env
+/.changelog.md
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 54229546..dd8e3259 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,18 +3,6 @@
 All notable changes to aerc will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
-## [Unreleased](https://git.sr.ht/~rjarry/aerc/log/master)
-
-### Added
-
-- New `flagged` criteria for `:sort`
-- New `:send-keys` command to control embedded terminals.
-- Account aliases now support fnmatch-style wildcards
-
-### Fixed
-
-- `colorize` styles can include wildcards `?` and `*`
-
 ## [0.16.0](https://git.sr.ht/~rjarry/aerc/refs/0.16.0) - 2023-09-27
 
 ### Added
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e06ac010..0ede7657 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -19,10 +19,6 @@ that you did not break anything.
 - If applicable, update unit tests.
 - If adding a new feature, please consider adding new tests.
 - Do not forget to update the docs.
-- If your commit brings visible changes for end-users, add an entry in the
-  *Unreleased* section of the
-  [CHANGELOG.md](https://git.sr.ht/~rjarry/aerc/tree/master/item/CHANGELOG.md)
-  file.
 - Run the linter using `make lint`.
 
 Once you are happy with your work, you can create a commit (or several
@@ -47,6 +43,18 @@ commits). Follow these general rules:
 - If you are fixing a regression introduced by another commit, add a `Fixes:`
   trailer with the commit id and its title.
 - When in doubt, follow the format and layout of the recent existing commits.
+- If your commit brings visible changes for end-users, add one of the following
+  trailers with a short and concise description of the change.
+
+  * `Changelog-added:` for new features.
+  * `Changelog-fixed:` for bug fixes.
+  * `Changelog-changed:` for behaviour or config format changes.
+  * `Changelog-deprecated:` for deprecation or removal of functionality.
+
+  If a complete trailer is longer than 72 characters, it can be continued by
+  indenting extra lines with a single space. The trailer text must be valid
+  markdown. You can take inspiration from existing entries in
+  [CHANGELOG.md](https://git.sr.ht/~rjarry/aerc/tree/master/item/CHANGELOG.md).
 
 There is a great reference for commit messages in the
 [Linux kernel documentation](https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes).
diff --git a/contrib/release.sh b/contrib/release.sh
index e3b3369c..001c68d2 100755
--- a/contrib/release.sh
+++ b/contrib/release.sh
@@ -13,7 +13,25 @@ tag_url="https://git.sr.ht/~rjarry/aerc/refs/$next_tag"
 
 echo "======= Creating release commit..."
 sed -i GNUmakefile -e "s/$prev_tag/$next_tag/g"
-sed -i CHANGELOG.md -e "s|^## \[Unreleased\].*|&\n\n## [$next_tag]($tag_url) - $(date +%Y-%m-%d)|"
+make wrap
+{
+	echo
+	echo "## [$next_tag]($tag_url) - $(date +%Y-%m-%d)"
+	for kind in Added Fixed Changed Deprecated; do
+		format="%(trailers:key=Changelog-$kind,unfold,valueonly)"
+		if git log --format="$format" $prev_tag.. | grep -q .; then
+			echo
+			echo "### $kind"
+			echo
+			git log --format="$format" $prev_tag.. | \
+				sed '/^$/d; s/[[:space:]]\+/ /; s/^/- /' | \
+				./wrap -r
+		fi
+	done
+} > .changelog.md
+sed -i CHANGELOG.md -e '/^The format is based on/ r .changelog.md'
+${EDITOR:-vi} CHANGELOG.md
+rm -f .changelog.md
 git add GNUmakefile CHANGELOG.md
 git commit -sm "Release version $next_tag"