docs: Tidy up release notes

Author: twpayne

assets/chezmoi.io/docs/reference/release-history.md.tmpl

@@ -1,13 +1,15 @@
 # Release history
-{{- range $release := gitHubListReleases "twpayne/chezmoi" }}
+
+{{- $releases := gitHubListReleases "twpayne/chezmoi" }}
+{{- $lastReleaseIndex := sub (len $releases) 1 }}
+{{- range $index, $release := $releases }}
 
 ## [{{ $release.Name | trimPrefix "v" }}]({{ $release.HTMLURL }}) ({{ $release.PublishedAt | gitHubTimestampFormat "2006-01-02" }})
 
 {{ $release.Body
-   | replaceAllRegex "(?m)^## What's Changed$" ""
-   | replaceAllRegex "(?m)^## Changelog\\r?$" ""
-   | replaceAllRegex "(?m)^## (New Contributors)\\r?$" "$1\n"
-   | replaceAllRegex "\\*\\*(Full Changelog)\\*\\*" "$1"
+   | replaceAllRegex "(?m)^#+ (Changelog\\r?|What's Changed)$" ""
+   | replaceAllRegex "(?m)^#+ (.*)\\r?$" "\n\n$1\n"
+   | replaceAllRegex "\\*\\*(Full Changelog)\\*\\*.*\n" ""
    | replaceAllRegex "(https://github\\.com/twpayne/chezmoi/compare/(\\S+))" "[`$2`]($1)"
    | replaceAllRegex "@(\\S+)" "[**$0**](https://github.com/$1)"
    | replaceAllRegex "pull request #(\\d+)" "pull request https://github.com/twpayne/chezmoi/pull/$1"
@@ -16,5 +18,14 @@
    | replaceAllRegex "(?m)^([0-9a-f]{7,})" "* $1"
    | replaceAllRegex "(?m)^\\* ([0-9a-f]{7,})" "* [`$1`](https://github.com/twpayne/chezmoi/commit/$1)"
    | replaceAllRegex "\\r\\n" "\\n"
+   | trim
+   | default "Internal changes only"
 }}
+
+{{- if ne $index $lastReleaseIndex }}
+{{-   $prevRelease := index $releases (add $index 1) }}
+
+Full changelog: [{{ $prevRelease.Name }}...{{ $release.Name }}](https://github.com/twpayne/chezmoi/compare/{{ $prevRelease.Name }}...{{ $release.Name }})
+{{- end }}
+
 {{- end }}