test-check-code: do not use xargs
We have too many files, and passing them via arguments could cause strange
errors on some platforms [1]. Since check-code.py can now take "-" and read
file names from stdin, use it instead of xargs to avoid the argv size limit.
[1]: https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-April/096346.html
$ cat >> $HGRCPATH << EOF
> [ui]
> logtemplate="{rev}:{node|short} ({phase}) [{tags} {bookmarks}] {desc|firstline}\n"
> [extensions]
> dirstateparanoidcheck = $TESTDIR/../contrib/dirstatenonnormalcheck.py
> [experimental]
> nonnormalparanoidcheck = True
> [devel]
> all-warnings=True
> EOF
$ mkcommit() {
> echo "$1" > "$1"
> hg add "$1"
> hg ci -m "add $1"
> }
$ hg init testrepo
$ cd testrepo
$ mkcommit a
$ mkcommit b
$ mkcommit c
$ hg status