hgweb: fix empty navigation detection

For some obscure reason, changelog.node(0) returns nullid if changelog is empty.
this break empty navigation detection. We fix this code by using the length of
the changelog.

Using the length have some issue with revision filtering but this is a small
step in the right direction. Proper fix comes in later changeset.

mercurial/hgweb/webutil.py

@@ -51,11 +51,7 b' class revnav(object):'
 
     def __nonzero__(self):
         """return True if any revision to navigate over"""
-        try:
-            self._revlog.node(0)
-            return True
-        except error.RepoError:
-            return False
+        return bool(len(self._revlog))
 
     def hex(self, rev):
         return hex(self._revlog.node(rev))

tests/test-hgweb-empty.t

@@ -70,7 +70,7 b' Some tests for hgweb in an empty reposit'
   <div class="navigate">
   <a href="/shortlog/-1?revcount=30">less</a>
   <a href="/shortlog/-1?revcount=120">more</a>
-  | rev -1: <a href="/shortlog/000000000000">(0)</a> <a href="/shortlog/tip">tip</a> 
+  | rev -1: 
   </div>
   
   <table class="bigtable">
@@ -85,7 +85,7 b' Some tests for hgweb in an empty reposit'
   <div class="navigate">
   <a href="/shortlog/-1?revcount=30">less</a>
   <a href="/shortlog/-1?revcount=120">more</a>
-  | rev -1: <a href="/shortlog/000000000000">(0)</a> <a href="/shortlog/tip">tip</a> 
+  | rev -1: 
   </div>
   
   </div>
@@ -97,6 +97,8 b' Some tests for hgweb in an empty reposit'
   </body>
   </html>
   
+  $ echo babar
+  babar
   $ ("$TESTDIR/get-with-headers.py" localhost:$HGPORT 'log')
   200 Script output follows
   
@@ -161,7 +163,7 b' Some tests for hgweb in an empty reposit'
   <div class="navigate">
   <a href="/shortlog/-1?revcount=5">less</a>
   <a href="/shortlog/-1?revcount=20">more</a>
-  | rev -1: <a href="/shortlog/000000000000">(0)</a> <a href="/shortlog/tip">tip</a> 
+  | rev -1: 
   </div>
   
   <table class="bigtable">
@@ -176,7 +178,7 b' Some tests for hgweb in an empty reposit'
   <div class="navigate">
   <a href="/shortlog/-1?revcount=5">less</a>
   <a href="/shortlog/-1?revcount=20">more</a>
-  | rev -1: <a href="/shortlog/000000000000">(0)</a> <a href="/shortlog/tip">tip</a> 
+  | rev -1: 
   </div>
   
   </div>
@@ -250,7 +252,7 b' Some tests for hgweb in an empty reposit'
   <div class="navigate">
   <a href="/graph/-1?revcount=30">less</a>
   <a href="/graph/-1?revcount=120">more</a>
-  | rev -1: <a href="/graph/000000000000">(0)</a> <a href="/graph/tip">tip</a> 
+  | rev -1: 
   </div>
   
   <noscript><p>The revision graph only works with JavaScript-enabled browsers.</p></noscript>
@@ -320,7 +322,7 b' Some tests for hgweb in an empty reposit'
   <div class="navigate">
   <a href="/graph/-1?revcount=30">less</a>
   <a href="/graph/-1?revcount=120">more</a>
-  | rev -1: <a href="/graph/000000000000">(0)</a> <a href="/graph/tip">tip</a> 
+  | rev -1: 
   </div>
   
   </div>