SOLR-17979 Improve release tooling during 9.10 release (#3808)

- Port tool parseContributorsFromChanges.py to use logchange
- Release Wizard improvements for 9.10.0:
  - support for persisting vars in commands
  - changed logchange steps
- Many improvements in the 1-time changes2logchange.py utility
- Bug fix changes2html.py to handle ALPHA/BETA releases
- New validateChangelogs.py tool

Author: janhoy

dev-docs/changelog.adoc

@@ -155,6 +155,91 @@ links:
   url: https://issues.apache.org/jira/browse/SOLR-17960
 ----
 
+=== 6.3 Changelog validation tool
+
+There is a tool `dev-tools/scripts/validateChangelogs.py` that will do a
+cross-branch validation of changelog folders. It takes no arguments and
+discovers the branch structure automatically, and checks that each branch
+(unstable, stable, release, previous-stable, previous-bugfix) are in sync
+with remote and "clean". Then it checks that the changelog folders are the
+same across branches and computes some statistics on how many unreleased
+features are from each branch.
+
+The tool can also output a consolidated `CHANGELOG.md` file which calculates
+what (unreleased) features are likely to be released in what version. This
+resembles what we used to have in our `CHANGES.txt` on main branch before.
+The tool is integrated in the releaseWizard.
+
+    usage: validateChangelogs.py -h
+
+Example report output (Json or Markdown):
+
+[source,json,title=Example json report]
+----
+{
+  "success": false,
+  "errors": [
+    "Folder v9.8.1 not found on branches: {'branch_9_9'}",
+    "Folder v9.9.0 not found on branches: {'branch_9_9'}"
+  ],
+  "warnings": [],
+  "branch_report": {
+    "branch_9_9": {
+      "version": "9.9.1",
+      "has_changelog_folder": false,
+      "id": "previous_major_bugfix"
+    },
+    "branch_9x": {
+      "version": "9.10.0",
+      "unreleased_count": 31,
+      "id": "previous_major_stable",
+      "new_count": 31,
+      "new": [
+        "SOLR-17541-deprecate -cloudhttp2solrclient-builder.yml",
+        "SOLR-17619 Use logchange for changelog management.yml"
+      ],
+      "not_in_newer_count": 1,
+      "not_in_newer": [
+        "SOLR-17541-deprecate -cloudhttp2solrclient-builder.yml"
+      ]
+    },
+    "branch_10_0": {
+      "version": "10.0.0",
+      "unreleased_count": 146,
+      "id": "release",
+      "new_count": 5,
+      "new": [
+        "GITHUB#3666-removing redundant check if field exists in.yml",
+        "SOLR-12089-remove deprecated -breaksugestiontiebreaker-.yml",
+        "SOLR-14070-deprecate cloudsolrclient-s zookeeper hosts.yml"
+      ],
+      "not_in_newer_count": 2,
+      "not_in_newer": [
+        "SOLR-16562-solr-16578- upgrade caffeine to 3-1-4 and.yml",
+        "SOLR-17012-update apache hadoop to 3-3-6 and apache curator.yml"
+      ]
+    },
+    "branch_10x": {
+      "version": "10.1.0",
+      "unreleased_count": 147,
+      "id": "stable",
+      "new_count": 2,
+      "new": [
+        "PR#3758-logs- removed webapp-solr and also removed from.yml",
+        "SOLR-17963-these solrcloud commands no longer aquire locks.yml"
+      ]
+    },
+    "main": {
+      "version": "11.0.0",
+      "unreleased_count": 147,
+      "id": "main",
+      "new_count": 0,
+      "new": []
+    }
+  }
+}
+----
+
 == 7. Further Reading
 
 * xref:https://github.com/logchange/logchange[Logchange web page]

dev-tools/scripts/README.md

@@ -182,6 +182,19 @@ Each YAML file complies with the schema outlined in `dev-docs/changelog.adoc`.
     # Default behavior
     python3 dev-tools/scripts/changes2logchange.py solr/CHANGES.txt
 
+### validateChangelogs.py
+
+Validates changelog folder structure and feature distribution across development branches (main, stable, release). See dev-docs for more.
+
+### parseContributorsFromChanges.py
+
+Extracts unique author names from all YAML changelog files in a version folder and outputs them as a comma-separated list sorted alphabetically. Used by RM to assemble release notes.
+
+    usage: parseContributorsFromChanges.py <version>
+
+    # Example: Extract contributors for version 9.10.0
+    python3 dev-tools/scripts/parseContributorsFromChanges.py 9.10.0
+
 ### gitignore-gen.sh
 
 TBD