CLDR-18209 spec: require modifications section to be updated (#5122)

Co-authored-by: Annemarie Apple <[email protected]>

Author: srl295

.github/workflows/maven.yml

@@ -60,6 +60,9 @@ jobs:
             output: linkcheck.md
       - name: Link Checker Summary PathDescriptions.md
         run: cat linkcheck.md >> $GITHUB_STEP_SUMMARY
+      - name: 'spec: Check that tr35-modifications.md was updated'
+        if: github.event_name == 'pull_request'
+        run: bash tools/scripts/tr-archive/check-mod-section.sh HEAD origin/${{ github.base_ref }}
   package:
     name: "Package up CLDR"
     runs-on: ubuntu-latest

docs/ldml/tr35-modifications.md

@@ -61,6 +61,10 @@ The LDML specification is divided into the following parts:
 
 ## Modifications
 
+<!--
+      Note: As of CLDR-18209, ALL changes to the spec require this file, tr35-modifications.md to be modified as well. If you are making a change that doesn't need to be noted, or is already noted, please simply add an HTML comment (such as this one) to the appropriate section.  The comment will not be visible to viewers of the HTML page.
+-->
+
 **Changes in LDML Version 48 (Differences from Version 47)**
 
 ### Locale Identifiers and Names
@@ -70,7 +74,7 @@ Also revamped the description of how to construct names for locale IDs, for clar
 * [Likely Subtags](tr35.md#likely-subtags) Changed the Canonicalize step to point to the section on canonicalization.
 * [Unicode Locale Identifier](tr35.md#unicode-locale-identifier) Changed the `attribute` component in the EBNF to be `uattribute` for consistency with `ufield`, etc.
 and to reduce confusion with XML attributes.
-  
+
 ### Misc.
 * [Character Elements](tr35-general.md#character-elements) Added new exemplar types.
 * [DTD Annotations](tr35.md#dtd_annotations) Added the @CDATA annotation, to indicate which elements are generated with @CDATA format
@@ -106,7 +110,7 @@ The rules have been converted to a “flat” format, which is easier for client
 
 ### MessageFormat
 * Syntax and data model errors must now be prioritized over other errors <!-- ([\#1011](https://github.com/unicode-org/message-format-wg/pull/1011)) -->
-* The Default Bidi Strategy is now required and default <!-- ([\#1066](https://github.com/unicode-org/message-format-wg/pull/1066)) --> 
+* The Default Bidi Strategy is now required and default <!-- ([\#1066](https://github.com/unicode-org/message-format-wg/pull/1066)) -->
 * The `:offset` function (previously named `:math`) is now available as Stable <!-- ([\#1073](https://github.com/unicode-org/message-format-wg/pull/1073)) -->
 * The `:datetime`, `:date`, and `:time` _draft_ functions are updated to build on top of semantic skeletons <!-- ([\#1078](https://github.com/unicode-org/message-format-wg/pull/1078), [\#1083](https://github.com/unicode-org/message-format-wg/pull/1083)) -->
 * `:percent` is added as a new _draft_ function <!-- ([\#1094](https://github.com/unicode-org/message-format-wg/pull/1094)) -->

tools/scripts/tr-archive/check-mod-section.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+
+function msg() {
+    if [[ ! -z "${GITHUB_STEP_SUMMARY}" ]];
+    then
+        echo "$@" >> "${GITHUB_STEP_SUMMARY}"
+    fi
+    echo "% $@"
+}
+
+
+if [[ $# -ne 2 ]];
+then
+    msg "X Internal Error"
+    echo >&2 "Error: usage: $0 ref1 ref2"
+    exit 1
+fi
+
+CHANGED=$(git diff --name-status $1 $2 | grep '^[MA]' | cut -c2- | fgrep 'docs/ldml/tr35-')
+
+if [[ -z "${CHANGED}" ]];
+then
+    msg "∅ No spec changes."
+    exit 0
+fi
+
+function list_changed() {
+    msg ""
+    msg "## List of changes:"
+    for file in ${CHANGED}; do
+        msg "- ${file}"
+    done
+    msg ""
+}
+
+if echo "${CHANGED}" | fgrep -s '/tr35-modifications.md';
+then
+    msg "✅ Spec changes: tr35-modifications.md was updated"
+    list_changed
+    exit 0
+else
+    msg "⚠️ Spec changes but tr35-modifications.md section was not updated!"
+    msg "For non-substantive changes that do not require an item in modifications such as fixing typos, add an HTML comment such as:"
+    msg ""
+    msg "     <!-- updated whitespace -->"
+    msg ""
+    msg "to the file."
+    list_changed
+    exit 1
+fi