Enhance "generate-stackbrew-library.sh" to only take into account changes to the Dockerfile or files from COPY in the Dockerfile for choosing the commit hash for a particular directory

Author: tianon

generate-stackbrew-library.sh

@@ -15,7 +15,7 @@ url='git://github.com/docker-library/mysql'
 echo '# maintainer: InfoSiftr <[email protected]> (@infosiftr)'
 
 for version in "${versions[@]}"; do
-	commit="$(git log -1 --format='format:%H' -- "$version")"
+	commit="$(cd "$version" && git log -1 --format='format:%H' -- Dockerfile $(awk 'toupper($1) == "COPY" { for (i = 2; i < NF; i++) { print $i } }' Dockerfile))"
 	fullVersion="$(grep -m1 'ENV MYSQL_VERSION ' "$version/Dockerfile" | cut -d' ' -f3)"
 	versionAliases=()
 	while [ "$fullVersion" != "$version" -a "${fullVersion%[.-]*}" != "$fullVersion" ]; do