chg: define _GNU_SOURCE to allow CentOS 5 compilation Without this flag, compilation fails with: hgclient.c: In function 'hgc_open': hgclient.c:466: error: 'O_DIRECTORY' undeclared (first use in this function) hgclient.c:466: error: (Each undeclared identifier is reported only once hgclient.c:466: error: for each function it appears in.) Differential Revision: https://phab.mercurial-scm.org/D260

#if no-windows no-osx

  $ mkdir -p xdgconf/hg
  $ echo '[ui]' > xdgconf/hg/hgrc
  $ echo 'username = foobar' >> xdgconf/hg/hgrc
  $ XDG_CONFIG_HOME="`pwd`/xdgconf" ; export XDG_CONFIG_HOME
  $ unset HGRCPATH
  $ hg config ui.username 2>/dev/null
  foobar

#endif