[PATCH 1 of 3 V3] localrepo.status: ignore empty symlink placeholders

[Siddharth Agarwal]

# HG changeset patch
# User Siddharth Agarwal <sid0 at fb.com>
# Date 1377969366 25200
#      Sat Aug 31 10:16:06 2013 -0700
# Node ID 37f868a08266f180b8474eef2667aaf76629aae1
# Parent  2f1c42f4d99372ab414bfdd68c6f946b73b696b3
localrepo.status: ignore empty symlink placeholders

A symlink's target should never be empty in normal use. Solaris and some BSDs
do allow empty symlinks to be created (with varying semantics on dereference),
but a symlink placeholder that started off as empty is either

- going to be empty, in which case ignoring it is fine, since it's unchanged, or
- going to not be empty, in which case this check is irrelevant.

diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -1557,7 +1557,7 @@
             for f in modified:
                 if ctx2.flags(f) == 'l':
                     d = ctx2[f].data()
-                    if len(d) >= 1024 or '\n' in d or util.binary(d):
+                    if d == '' or len(d) >= 1024 or '\n' in d or util.binary(d):
                         self.ui.debug('ignoring suspect symlink placeholder'
                                       ' "%s"\n' % f)
                         continue
diff --git a/tests/test-symlink-placeholder.t b/tests/test-symlink-placeholder.t
--- a/tests/test-symlink-placeholder.t
+++ b/tests/test-symlink-placeholder.t
@@ -41,6 +41,13 @@
   a (no-eol)
   $ hg --config extensions.n=$TESTTMP/nolink.py st --debug
 
+Empty placeholder:
+
+  $ rm b
+  $ touch b
+  $ hg --config extensions.n=$TESTTMP/nolink.py st --debug
+  ignoring suspect symlink placeholder "b"
+
 Write binary data to the placeholder:
 
   >>> open('b', 'w').write('this is a binary\0')