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
Test for changeset ba7c74081861
(update dirstate correctly for non-branchmerge updates)
$ hg init a
$ cd a
$ echo a > a
$ hg add a
$ hg commit -m a
$ cd ..
$ hg clone a b
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd a
$ hg mv a b
$ hg commit -m move
$ echo b >> b
$ hg commit -m b
$ cd ../b
$ hg pull ../a
pulling from ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
(run 'hg update' to get a working copy)
$ hg update
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cd ..