Support AsciiDoc-style headings ( = instead of #)

[sdavids]

$ ./gradlew --version

------------------------------------------------------------
Gradle 8.12
------------------------------------------------------------

Build time:    2024-12-20 15:46:53 UTC
Revision:      a3cacb207fec727859be9354c1937da2e59004c1

Kotlin:        2.0.21
Groovy:        3.0.22
Ant:           Apache Ant(TM) version 1.10.15 compiled on August 25 2024
Launcher JVM:  17.0.13 (Eclipse Adoptium 17.0.13+11)
Daemon JVM:    Compatible with Java 17, Eclipse Temurin (from gradle/gradle-daemon-jvm.properties)
OS:            Mac OS X 12.7.6 x86_64

$ cat gradle/libs.versions.toml | grep spotlessChangelog
spotlessChangelog = "com.diffplug.spotless-changelog:3.1.2"
$ cat CHANGELOG.adoc 
= Changelog

== [Unreleased]
$ ./gradlew changelogCheck                              
> Task :changelogCheck FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':changelogCheck'.
> CHANGELOG.adoc: Needs to have '## [Unreleased]'

---

https://docs.asciidoctor.org/asciidoc/latest/sections/titles-and-levels/#section-level-syntax

The number of equal signs in the marker represents the section level using a 0-based index

In addition to the equals sign marker used for defining section titles, Asciidoctor recognizes the hash symbol (#) from Markdown.

[nedtwigg]

Happy to take a PR for this.

• https://github.com/diffplug/spotless-changelog/blob/main/spotless-changelog-lib/src/main/java/com/diffplug/spotless/changelog/Changelog.java

[sdavids]

Would you like a simple fix, i.e. allow both # and =.

Or a more involved one via looking at the file extension of changelogFile or via a new DSL property changelogFormat or something similar.

[nedtwigg]

Simplicity is best! I'd prefer no new DSL property, but if adding one makes the implementation simpler it would be acceptable.

[sdavids]

What should happen with the error messages?

All of them assume ## [...].

One could keep the error messages as is and silently also accept == [...] or we would need to parameterize Changelog with a type (markdown/asciidoc) and then produce appropriate error messages.

The type would be determined via the file's extension.

[nedtwigg]

My preference is to parameterize with an enum, determined based on the file extension. Error messages can take that same enum as an argument.