shellcheck: introduce the --shellcheck-batch option

... to configure maximum number of scripts scanned by a single
shellcheck process

Related: https://issues.redhat.com/browse/OSH-655

py/plugins/shellcheck.py

@@ -27,6 +27,9 @@
 FILTER_CMD = "csgrep --mode=json --remove-duplicates --quiet " \
         "--invert-match --event '^note|warning\\[SC1090\\]'"
 
+# default maximum number of scripts scanned by a single shellcheck process
+DEFAULT_SC_BATCH = 1
+
 # default maximum amount of wall-clock time taken by a single shellcheck process [s]
 DEFAULT_SC_TIMEOUT = 30
 
@@ -51,6 +54,10 @@ def enable(self):
 
     def init_parser(self, parser):
         csmock.common.util.install_script_scan_opts(parser, "shellcheck")
+        parser.add_argument(
+            "--shellcheck-batch", type=int, default=DEFAULT_SC_BATCH,
+            help="maximum number of scripts scanned by a single shellcheck process" \
+                f" (defaults to {DEFAULT_SC_BATCH})")
         parser.add_argument(
             "--shellcheck-timeout", type=int, default=DEFAULT_SC_TIMEOUT,
             help="maximum amount of wall-clock time taken by a single shellcheck process [s]" \
@@ -69,6 +76,7 @@ def handle_args(self, parser, args, props):
 
         props.install_pkgs += ["ShellCheck"]
         cmd = f"SC_RESULTS_DIR={SHELLCHECK_CAP_DIR} "
+        cmd += f"SC_BATCH={args.shellcheck_batch} "
         cmd += f"SC_TIMEOUT={args.shellcheck_timeout} "
         cmd += f"{RUN_SHELLCHECK_SH} {dirs_to_scan}"
         props.post_build_chroot_cmds += [cmd]

scripts/run-shellcheck.sh

@@ -2,7 +2,8 @@
 export LC_ALL="C"
 
 # how many shell scripts we pass to shellcheck at a time
-export SC_BATCH=1
+test -n "$SC_BATCH" || export SC_BATCH=1
+test 0 -lt "$SC_BATCH" || exit $?
 
 # how many shellcheck processes we run in parallel
 SC_JOBS=$(getconf _NPROCESSORS_ONLN 2>/dev/null || echo 1)