bdiff: fix malloc(0) issue in fixws()
If fixws() is called on a zero-length string, malloc(0) is called and
expected to return a pointer. Which it does on e.g. Linux. AIX returns
NULL, which it is also legal, but the malloc() is then assumed to have
failed. So ensure a valid pointer is always returned.
http://mercurial.selenic.com/bts/issue1175
$ hg init
$ touch a
$ hg ci -Am0
adding a
$ hg mv a a1
$ hg ci -m1
$ hg co 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg mv a a2
$ hg up
note: possible conflict - a was renamed multiple times to:
a2
a1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg ci -m2
$ touch a
$ hg ci -Am3
adding a
$ hg mv a b
$ hg ci -Am4 a
$ hg ci --debug --traceback -Am5 b
b
b: searching for copy revision for a
b: copy a:b80de5d138758541c5f05265ad144ab9fa86d1db
committed changeset 5:89e8e4be0de296fa3d6dd7825ccc44d7dc0f1f3b
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
4 files, 6 changesets, 4 total revisions
$ hg export --git tip
# HG changeset patch
# User test
# Date 0 0
# Node ID 89e8e4be0de296fa3d6dd7825ccc44d7dc0f1f3b
# Parent 7fc86ba705e717a721dbc361bf8c9bc05a18ca2f
5
diff --git a/b b/b
new file mode 100644