Add lastmod, last modified date of the bibliographic entry (#302)

lastmod is used in the sitemap to help identify files that have changed
and should be recrawled.  Writing lastmod into the markdown file's
YAML will ensure it takes presidence over the current date field,
which represents the publication date of the item, not the last
time the bibliographic entry was modified.

Author: stumbo

scripts/bibSplit.pl

@@ -103,7 +103,9 @@ sub sanitize_text {
 
   my $urlSource = defined $obj->{url} ? $obj->{url} : '';
 
-  # Some/most/all of these *may* need sanitize_text
+  # Modified date
+  my $dateModified = defined $obj->{dateModified} ? $obj->{dateModified} : '';
+
   # optional fields - ones used vary by value of type
   my $applicationNumber = defined $obj->{applicationNumber} ? qq{"$obj->{applicationNumber}"} : '""';
   my $assignee = defined $obj->{assignee} ? qq{"$obj->{assignees}"} : '""';
@@ -185,6 +187,9 @@ sub sanitize_text {
 tags:
 url_source: $urlSource
 zotero_url: "https://www.zotero.org/groups/2914042/items/$key"
+
+# Timestamp of last modification to bibliographic item
+lastmod: $dateModified
 ---
 
 ENDITEM

scripts/update_bibliography.sh

@@ -282,7 +282,7 @@ fi
 
 # Remove library, links, and meta objects; and some fields from entries
 # (These are not used any further on, so simplify.)
-items=$(jq 'map(del(.["library", "links", "meta", "accessed", "accessDate", "dateAdded", "dateModified"]))' <<< "$items")
+items=$(jq 'map(del(.["library", "links", "meta", "accessed", "accessDate", "dateAdded"]))' <<< "$items")
 showInfo 8 "Remove library, links, and meta objects and some unnecessary fields"
 if $debugFiles ; then
   dfn=$(debugFileName "noLibraryLinksMeta" $dfn)