githooks: add check for file size into pre-commit hook

.githooks/pre-commit

@@ -5,6 +5,10 @@
 #
 set -eu
 
+# Maximal allowed size (in bytes) of a file.
+FILE_SIZE_LIMIT=262144  # 256 kiB
+
+
 if ! command -v sha512sum >/dev/null; then
 	# macOS / BSDs (?) don't have sha512sum, but shasum.
 	alias sha512sum='shasum -a 512'
@@ -14,13 +18,13 @@ error() {
 	printf '\033[0;31mpre-commit:\033[0m %s\n' "$1" >&2  # red
 }
 
-# Prints paths of created or modified APKBUILDs being committed.
-changed_apkbuilds() {
+# Prints paths of created or modified files being committed.
+changed_files() {
 	git diff-index \
 		--name-only \
 		--cached \
 		--diff-filter=ACMR HEAD \
-		-- '**/APKBUILD'
+		-- "$@"
 }
 
 # Prints file names and checksums (in format <SHA-512>:<filename>) of local
@@ -79,7 +83,25 @@ check_local_sources() {
 	return $status
 }
 
+# Checks if the file ($1) being committed is not bigger than FILE_SIZE_LIMIT.
+check_file_size() {
+	local path="$1"
+	local size
+
+	size=$(git cat-file -s ":$path")
+	if [ $size -gt $FILE_SIZE_LIMIT ]; then
+		local size_kb=$(( size / 1024 ))
 
-for apkbuild in $(changed_apkbuilds); do
+		error "file \"$path\" is quite big ($(( size / 1024 )) kiB), better to upload it to dev.alpinelinux.org"
+		return 1
+	fi
+}
+
+
+for apkbuild in $(changed_files '**/APKBUILD'); do
 	check_local_sources "$apkbuild"
 done
+
+for path in $(changed_files); do
+	check_file_size "$path"
+done