Add --last-push-hash option to deploy-ebook-to-www script to decide whether to rebuild the cover images/actual ebook

scripts/deploy-ebook-to-www

@@ -6,12 +6,14 @@ DESCRIPTION
 	Deploy a Standard Ebook source repository to the web.
 
 USAGE
-	deploy-ebook-to-www [-v,--verbose] [-g,--group GROUP] [--webroot WEBROOT] [--weburl WEBURL] [--no-images] DIRECTORY [DIRECTORY...]
+	deploy-ebook-to-www [-v,--verbose] [-g,--group GROUP] [--webroot WEBROOT] [--weburl WEBURL] [--no-images] [-l,--last-push-hash HASH] DIRECTORY [DIRECTORY...]
 		DIRECTORY is a bare source repository.
 		GROUP is a groupname. Defaults to "se".
 		WEBROOT is the path to your webroot. Defaults to "/standardebooks.org".
 		WEBURL is the URL the website is served on. Defaults to "https://standardebooks.org".
 
+		With --last-push-hash, check the repo head against HASH to see if the cover image or ebook source changed, which will determine if cover thumbnails get re-generated or the ebook gets re-built.
+
 		With --no-images, do not create cover thumbnails or hero images for the web.
 EOF
 	exit
@@ -22,9 +24,11 @@ require(){ command -v "$1" > /dev/null 2>&1 || { suggestion=""; if [ -n "$2" ];
 
 verbose="false"
 images="true"
+build="true"
 group="se"
 webRoot="/standardebooks.org/web"
 webUrl="https://standardebooks.org"
+lastPushHash=""
 
 if [ $#  -eq 0 ]; then
 	usage
@@ -53,6 +57,11 @@ while [ $# -gt 0 ]; do
 			webUrl="$2"
 			shift 2
 			;;
+		-l|--last-push-hash)
+			[ -n "$2" ] || die "Last commit hash can’t be empty."
+			lastPushHash="$2"
+			shift 2
+			;;
 		--no-images)
 			images="false"
 			shift 1
@@ -124,6 +133,25 @@ do
 		continue
 	fi
 
+	if [ "${lastPushHash}" != "" ]; then
+		# We were passed the hash of the last push before this one.
+		# Check to see if the cover image changed, to decide if we want to rebuild the cover image thumbnail/hero
+		diff=$(git diff "${lastPushHash}" HEAD)
+
+		if [[ "${diff}" =~ diff\ --git\ a/images/cover.jpg ]] || [[ "${diff}" =~ diff\ --git\ a/images/cover.svg ]]; then
+			images="true"
+		else
+			images="false"
+		fi
+
+		# Check to see if the actual ebook changed, to decide if we want to build
+		if [[ "${diff}" =~ diff\ --git\ a/src/ ]]; then
+			build="true"
+		else
+			build="false"
+		fi
+	fi
+
 	webDir=$(git show HEAD:src/epub/content.opf | grep --only-matching --extended-regexp "<dc:identifier id=\"uid\">url:https://standardebooks.org/ebooks/[^<]+<\/dc:identifier>" | sed --regexp-extended "s/<[^>]+?>//g" | sed --regexp-extended "s/^url:https:\/\/standardebooks.org\/ebooks\/?//")
 
 	if [ "${webDir}" = "" ]; then
@@ -183,6 +211,7 @@ do
 		popd > /dev/null || die "Couldn't pop directory."
 	fi
 
+	if [ "${build}" = "true" ]; then
 		if [ "${verbose}" = "true" ]; then
 			printf "Building ebook ... "
 		fi
@@ -214,6 +243,7 @@ do
 
 		# Move contents of the work dir over
 		mv "${workDir}"/* "${webDir}/"
+	fi
 
 	if [ "${images}" = "true" ]; then
 		# Move the cover images over