feat: create last-modified mapping

Whenever this package is built in CI a module
`modules/frus.xqm` is added to the built XAR.

This can then be used to optimize caching in hsg-shell.

.github/workflows/build.yml

@@ -30,7 +30,11 @@ jobs:
         run: |
           mkdir -p frus-toc 
           java -jar /usr/share/java/Saxon-HE.jar -s:volumes/ -xsl:modules/lib/frus-toc.xsl -o:frus-toc/ -it:main
-      
+
+      - name: Create frus.xqm
+        run: |
+          ./create-last-modified-module.sh bibliography/* volumes/* > modules/frus.xqm
+
       # sanity check
       - name: What happened
         run: git status

create-last-modified-module.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+# -----------------------------------------------------------------------------
+# create an XQuery module
+# exporting a map mapping relative file paths to their last commit date
+
+# -----------------------------------------------------------------------------
+# USAGE:
+# ./create-last-modified-module.sh volumes/* bibliography/* > modules/frus.xqm
+
+# -----------------------------------------------------------------------------
+# build list of mappings
+
+# helper function
+# USAGE: join $separator $list
+function join {
+    echo -n "$2"
+    [[ $# -gt 2 ]] && printf "$1%s" "${@:3}"
+}
+
+list=()
+
+for file in "${@}"
+do
+    iso=`git log -1 --format=%cd --date=iso-strict-local "$file"`
+    list+="    '$file': xs:dateTime('$iso')"
+done
+
+# -----------------------------------------------------------------------------
+# output module
+
+echo 'module namespace frus="http://history.state.gov/ns/site/frus/last-modified";'
+echo "\n"
+echo 'declare variable $frus:lm := map{';
+join ",\n" $list
+echo "\n};"