Add initial jq-based templating engine

[tianon]

See also docker-library/php#1052 (and linked PRs).

(This will make test builds a lot less taxing on our poor overworked @docker-library-bot ❤️)

[tianon]

`versions.sh` Diff:

$ git log -p -1 --find-copies-harder --follow -- versions.sh
commit aa3300462176c6ccaff3334d03af59ddc43caea2 (HEAD -> jq-template, infosiftr/jq-template)
Author: Tianon Gravi <[email protected]>
Date:   Fri Apr 9 16:41:16 2021 -0700

    Add initial jq-based templating engine

diff --git a/update.sh b/versions.sh
similarity index 82%
copy from update.sh
copy to versions.sh
index 927bb08..ff07159 100755
--- a/update.sh
+++ b/versions.sh
@@ -11,6 +11,9 @@ cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"
 versions=( "$@" )
 if [ ${#versions[@]} -eq 0 ]; then
 	versions=( */ )
+	json='{}'
+else
+	json="$(< versions.json)"
 fi
 versions=( "${versions[@]%/}" )
 
@@ -34,8 +37,9 @@ for version in "${versions[@]}"; do
 	lastModified="$(grep -Em1 '<a href="(gcc-)?'"$fullVersion"'/"' <<<"$packages" | awk -F '  +' '{ print $2 }')"
 	lastModified="$(date -d "$lastModified" +"$dateFormat")"
 
-	releaseAge="$(( $today - $(date +'%s' -d "$lastModified") ))"
-	if [ $releaseAge -gt $eolAge ]; then
+	lastModifiedTime="$(date +'%s' -d "$lastModified")"
+	releaseAge="$(( today - lastModifiedTime ))"
+	if [ "$releaseAge" -gt "$eolAge" ]; then
 		eols+=( "$version ($fullVersion)" )
 	fi
 	eolDate="$(date -d "$lastModified + $eolPeriod" +"$dateFormat")"
@@ -59,14 +63,16 @@ for version in "${versions[@]}"; do
 
 	echo "$version: $fullVersion ($lastModified vs $eolDate); $debianSuite, $compression"
 
-	sed -r \
-		-e 's!%%SUITE%%!'"$debianSuite"'!g' \
-		-e 's!^(ENV GCC_VERSION) .*!\1 '"$fullVersion"'!' \
-		-e 's!^(# Last Modified:) .*!\1 '"$lastModified"'!' \
-		-e 's!^(# Docker EOL:) .*!\1 '"$eolDate"'!' \
-		-e 's!%%TARBALL-COMPRESSION%%!'"$compression"'!g' \
-		Dockerfile.template \
-		> "$version/Dockerfile"
+	export version fullVersion lastModified eolDate debianSuite compression
+	json="$(jq <<<"$json" -c '
+		.[env.version] = {
+			version: env.fullVersion,
+			lastModified: env.lastModified,
+			eol: env.eolDate,
+			debian: env.debianSuite,
+			compression: env.compression,
+		}
+	')"
 done
 
 if [ ${#eols[@]} -gt 0 ]; then
@@ -84,3 +90,5 @@ if [ ${#eols[@]} -gt 0 ]; then
 		echo
 	} >&2
 fi
+
+jq <<<"$json" -S . > versions.json

`generate-stackbrew-library.sh` Diff:

$ diff -u <(bashbrew cat gcc) <(bashbrew cat <(./generate-stackbrew-library.sh))
--- /dev/fd/63	2021-04-09 16:44:22.238402544 -0700
+++ /dev/fd/62	2021-04-09 16:44:22.238402544 -0700
@@ -3,15 +3,15 @@
 
 Tags: 10.3.0, 10.3, 10, latest
 Architectures: amd64, arm32v5, arm32v7, arm64v8, ppc64le, s390x
-GitCommit: 15b89bbc6190e30a0dd657473e0cc9bfbd13610d
+GitCommit: aa3300462176c6ccaff3334d03af59ddc43caea2
 Directory: 10
 
 Tags: 9.3.0, 9.3, 9
 Architectures: amd64, arm32v5, arm32v7, arm64v8, ppc64le, s390x
-GitCommit: 05aef2fc627328e12bbf77aca44fd399a22c7fc4
+GitCommit: aa3300462176c6ccaff3334d03af59ddc43caea2
 Directory: 9
 
 Tags: 8.4.0, 8.4, 8
 Architectures: amd64, arm32v5, arm32v7, arm64v8, ppc64le, s390x
-GitCommit: 05aef2fc627328e12bbf77aca44fd399a22c7fc4
+GitCommit: aa3300462176c6ccaff3334d03af59ddc43caea2
 Directory: 8

Again With Comments Diff:

$ diff -u <(wget -qO- 'https://github.com/docker-library/official-images/raw/master/library/gcc') <(./generate-stackbrew-library.sh)
--- /dev/fd/63	2021-04-09 16:45:22.404751777 -0700
+++ /dev/fd/62	2021-04-09 16:45:22.404751777 -0700
@@ -1,4 +1,4 @@
-# this file is generated via https://github.com/docker-library/gcc/blob/7f1fc5e8be598446b2546b808572db546e959643/generate-stackbrew-library.sh
+# this file is generated via https://github.com/docker-library/gcc/blob/aa3300462176c6ccaff3334d03af59ddc43caea2/generate-stackbrew-library.sh
 
 Maintainers: Tianon Gravi <[email protected]> (@tianon),
              Joseph Ferguson <[email protected]> (@yosifkit)
@@ -7,20 +7,20 @@
 # Last Modified: 2021-04-08
 Tags: 10.3.0, 10.3, 10, latest
 Architectures: amd64, arm32v5, arm32v7, arm64v8, ppc64le, s390x
-GitCommit: 15b89bbc6190e30a0dd657473e0cc9bfbd13610d
+GitCommit: aa3300462176c6ccaff3334d03af59ddc43caea2
 Directory: 10
 # Docker EOL: 2022-10-08
 
 # Last Modified: 2020-03-12
 Tags: 9.3.0, 9.3, 9
 Architectures: amd64, arm32v5, arm32v7, arm64v8, ppc64le, s390x
-GitCommit: 05aef2fc627328e12bbf77aca44fd399a22c7fc4
+GitCommit: aa3300462176c6ccaff3334d03af59ddc43caea2
 Directory: 9
 # Docker EOL: 2021-09-12
 
 # Last Modified: 2020-03-04
 Tags: 8.4.0, 8.4, 8
 Architectures: amd64, arm32v5, arm32v7, arm64v8, ppc64le, s390x
-GitCommit: 05aef2fc627328e12bbf77aca44fd399a22c7fc4
+GitCommit: aa3300462176c6ccaff3334d03af59ddc43caea2
 Directory: 8
 # Docker EOL: 2021-09-04