import-checker: add xargs like mode Before this patch, "import-check.py" is invoked via "xargs" in "test-module-imports.t", but it doesn't ensure that "import-checker.py" is certainly invoked with all mercurial specific files at once. "xargs" may invoke specified command multiple times with part of arguments given from stdin: according to "xargs(1)" man page, this dividing arguments is system-dependent. This patch adds "xargs" like mode to "import-checker.py". This can ensure that "import-checker.py" is certainly invoked with all mercurial specific files at once in "test-module-imports.t". This is assumed by subsequent patches.