Add a tool to maintain a local pacman repository mirror

This tool will help us to upload new package releases to our Pacman
repository (which is currently moving to Bintray).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

pacman-mirror.sh

@@ -0,0 +1,195 @@
+#!/bin/sh
+
+# This script helps Git for Windows developers to manage their Pacman
+# repository.
+#
+# A Pacman repository is like a Git repository, but for binary packages.
+#
+# This script supports two commands:
+#
+# - 'fetch' to initialize (or update) a local mirror of the Pacman repository
+#
+# - 'push' to synchronize local changes (after calling `repo-add`) to the
+#   remote Pacman repository
+
+die () {
+	echo "$*" >&2
+	exit 1
+}
+
+mode=
+case "$1" in
+fetch|push)
+	mode="$1"
+	shift
+	;;
+*)
+	die "Usage: $0 ( fetch | push )"
+	;;
+esac
+
+base_url=https://dl.bintray.com/git-for-windows/pacman/msys2
+api_url=https://api.bintray.com
+content_url=$api_url/content/git-for-windows/pacman
+packages_url=$api_url/packages/git-for-windows/pacman
+mirror=/var/local/pacman-mirror
+
+architectures="i686 x86_64"
+
+arch_dir () { # architecture
+	echo "$mirror/$1"
+}
+
+fetch () {
+	for arch in $architectures
+	do
+		dir="$(arch_dir $arch)"
+		mkdir -p "$dir"
+		(cd "$dir" &&
+		 curl -sO $base_url/$arch/git-for-windows.db.tar.xz &&
+		 for name in $(package_list git-for-windows.db.tar.xz)
+		 do
+			filename=$name-$arch.pkg.tar.xz
+			test -f $filename ||
+			curl -sO $base_url/$arch/$filename ||
+			exit
+		 done ||
+		 exit
+		)
+	done
+}
+
+upload () { # <package> <version> <arch> <filename>
+	curl --netrc -T "$4" "$content_url/$1/$2/msys2/$3/$4"
+}
+
+publish () { # <package> <version>
+	curl --netrc -X POST "$content_url/$1/$2/publish"
+}
+
+
+delete_version () { # <package> <version>
+	curl --netrc -X DELETE "$packages_url/$1/versions/$2"
+}
+
+package_list () { # db.tar.xz
+	tar tf "$1" |
+	sed -n 's/\/$//p'
+}
+
+package_exists () { # package-name
+	case "$(curl --netrc -s "$packages_url/$1")" in
+	*\"name\":\""$1"\"*)
+		return 0
+		;;
+	*)
+		echo "Package $1 does not yet exist" >&2
+		return 1
+		;;
+	esac
+}
+
+db_version () {
+	json="$(curl --netrc -s \
+		"$packages_url/package-database/versions/_latest")"
+	latest="$(expr "$json" : '.*"name":"\([^"]*\)".*')"
+	test -n "$latest" ||
+	die "Could not determine latest version"
+
+	echo "$latest"
+}
+
+next_db_version () { # old version
+	today="$(date -u +%Y-%m-%d)"
+	case "$1" in
+	$today-*)
+		echo $today-$((${1##*-}+1))
+		;;
+	*)
+		echo $today-1
+		;;
+	esac
+}
+
+push () {
+	for arch in $architectures
+	do
+		dir="$(arch_dir $arch)"
+		mkdir -p "$dir"
+		(cd "$dir" &&
+		 curl -s $base_url/$arch/git-for-windows.db.tar.xz > .remote
+		) || exit
+	done
+
+	old_list="$((for arch in $architectures
+		do
+			package_list "$(arch_dir $arch)/.remote"
+		done) |
+		sort | uniq)"
+	new_list="$((for arch in $architectures
+		do
+			package_list "$(arch_dir $arch)/git-for-windows.db.tar.xz"
+		done) |
+		sort | uniq)"
+
+	to_upload="$(printf "%s\n%s\n%s\n" "$old_list" "$old_list" "$new_list" |
+		sort | uniq -u)"
+
+	test -n "$to_upload" || {
+		echo "Nothing to be done" >&2
+		return
+	}
+
+	to_upload_basenames="$(echo "$to_upload" |
+		sed 's/-[0-9].*//' |
+		sort | uniq)"
+
+	db_version="$(db_version)"
+	next_db_version="$(next_db_version "$db_version")"
+
+	# Verify that the packages exist already
+	for basename in $to_upload_basenames
+	do
+		case " $(echo "$old_list" | tr '\n' ' ')" in
+		*" $basename"-[0-9]*)
+			;;
+		*)
+			package_exists $basename ||
+			die "The package $basename does not yet exist..."
+			;;
+		esac
+	done
+
+	for name in $to_upload
+	do
+		basename=${name%%-[0-9]*}
+		version=${name#$basename-}
+		for arch in $architectures
+		do
+			filename=$name-$arch.pkg.tar.xz
+			(cd "$(arch_dir $arch)" &&
+			 if test -f $filename
+			 then
+				upload $basename $version $arch $filename
+			 fi) || exit
+		done
+		publish $basename $version
+	done
+
+	delete_version package-database "$db_version"
+
+	for arch in $architectures
+	do
+		(cd "$(arch_dir $arch)" &&
+		 for suffix in db db.tar.xz files files.tar.xz
+		 do
+			filename=git-for-windows.$suffix
+			test ! -f $filename ||
+			upload package-database $next_db_version $arch $filename
+		 done
+		) || exit
+	done
+	publish package-database $next_db_version
+}
+
+eval "$mode" "$@"