raise RevlogError when parser can't parse the revlog index

Initial patch and test thanks to Nicolas Dumazet.

mercurial/revlog.py

@@ -450,7 +450,10 b' class revlog(object):'
         if self.version == REVLOGV0:
             self._io = revlogoldio()
         if i:
+            try:
             d = self._io.parseindex(f, self._inline)
+            except (ValueError, IndexError), e:
+                raise RevlogError(_("index %s is corrupted") % (self.indexfile))
             self.index, self.nodemap, self._chunkcache = d
 
         # add the magic null revision at -1 (if it hasn't been done already)

tests/test-verify

@@ -1,7 +1,8 b''
 #!/bin/sh
 
 echo % prepare repo
-hg init
+hg init a
+cd a
 echo "some text" > FOO.txt
 echo "another text" > bar.txt
 echo "more text" > QUICK.txt
@@ -23,4 +24,22 b' echo'
 echo % verify
 hg verify
 
+cd ..
+
+echo % test revlog corruption
+hg init b
+cd b
+
+touch a
+hg add a
+hg ci -m a
+
+echo 'corrupted' > b
+head -c 20 .hg/store/data/a.i > start
+cat start b > .hg/store/data/a.i
+
+echo
+echo % verify
+hg verify
+
 exit 0

tests/test-verify.out

@@ -29,3 +29,16 b' checking files'
 3 files, 1 changesets, 0 total revisions
 9 integrity errors encountered!
 (first damaged changeset appears to be 0)
+% test revlog corruption
+
+% verify
+checking changesets
+checking manifests
+crosschecking files in changesets and manifests
+checking files
+ a@0: broken revlog! (index data/a.i is corrupted)
+warning: orphan revlog 'data/a.i'
+1 files, 1 changesets, 0 total revisions
+1 warnings encountered!
+1 integrity errors encountered!
+(first damaged changeset appears to be 0)