Tweak build/clone logic to always do a checkout, and to bail gracefully when a commit doesn't exist (skipping the relevant repoTag build)

build.sh

@@ -193,8 +193,12 @@ while [ "$#" -gt 0 ]; do
 	
 	echo "Processing $repoTag ..."
 	
-	if [ "$doClone" ]; then
-		( cd "$gitRepo" && git clean -dfxq && git checkout -q "$gitRef" && "$dir/git-set-dir-times" )
+	if ! ( cd "$gitRepo" && git rev-parse --verify "${gitRef}^{commit}" &> /dev/null ); then
+		echo "- skip; invalid ref: $gitRef"
+		continue
+	fi
+	
+	( cd "$gitRepo" && git clean -dfxq && git checkout -q "$gitRef" )
 	# TODO git tag
 	
 	IFS=$'\n'
@@ -211,9 +215,10 @@ while [ "$#" -gt 0 ]; do
 			fi
 		done
 	done
-	fi
 	
 	if [ "$doBuild" ]; then
+		( cd "$gitRepo/$gitDir" && "$dir/git-set-dir-times" )
+		
 		thisLog="$logDir/build-$repoTag.log"
 		touch "$thisLog"
 		ln -sf "$thisLog" "$latestLogDir/$(basename "$thisLog")"