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

@@ -7,7 +7,7 @@ url='git://github.com/docker-library/celery'
 
 echo '# maintainer: InfoSiftr <[email protected]> (@infosiftr)'
 
-commit="$(git log -1 --format='format:%H' -- .)"
+commit="$(git log -1 --format='format:%H' -- Dockerfile $(awk 'toupper($1) == "COPY" { for (i = 2; i < NF; i++) { print $i } }' Dockerfile))"
 fullVersion="$(grep -m1 'ENV CELERY_VERSION ' Dockerfile | cut -d' ' -f3)"
 
 versionAliases=()