Make checksum command operating system based

src/_utils/_git_secret_tools.sh

@@ -15,7 +15,7 @@ _SECRETS_DIR_PATHS_MAPPING="${_SECRETS_DIR_PATHS}/mapping.cfg"
 
 # Commands:
 : "${SECRETS_GPG_COMMAND:="gpg"}"
-: "${SECRETS_CHECKSUM_COMMAND:="sha256sum"}"
+: "${SECRETS_CHECKSUM_COMMAND:="_os_based __sha256"}"
 
 
 # AWK scripts:

src/_utils/_git_secret_tools_linux.sh

@@ -12,3 +12,7 @@ function __temp_file_linux {
   filename=$(mktemp)
   echo "$filename"
 }
+
+function __sha256_linux {
+  sha256sum "$1"
+}

src/_utils/_git_secret_tools_osx.sh

@@ -13,3 +13,8 @@ function __temp_file_osx {
   filename=$(mktemp -t _gitsecrets_XXX )
   echo "$filename";
 }
+
+
+function __sha256_osx {
+  /usr/bin/shasum -a256 "$1"
+}