hiddenerror: fix out of bounds error

Summary:
The current code checks if the filter error reports a rev number, and if it does
tries to convert it to a node. If the 'number' is actually just a short form of
a hash that happens to be all digits, then it may be a number greater than the
size of the changelog, so we need to not attempt to access it in the changelog,
otherwise we get an IndexError.

Test Plan: Added a test, it failed before with a weird error

Reviewers: #mercurial, kulshrax

Reviewed By: kulshrax

Subscribers: mjpieters

Differential Revision: https://phabricator.intern.facebook.com/D4613988

Signature: t1:4613988:1488027938:4f5ffcb07aeecbaf59cad20fb3a592dd92ed2beb

hgext3rd/hiddenerror.py

@@ -41,7 +41,14 @@ def uisetup(ui):
                     raise
 
                 rev = int(match.group(1))
-                node = repo.unfiltered().changelog.node(rev)
+                cl = repo.unfiltered().changelog
+
+                # If the number is beyond the changelog, it's a short hash that
+                # just happened to be a number.
+                if rev >= len(cl):
+                    raise
+
+                node = cl.node(rev)
                 shorthash = short(node)
 
                 # Get the error messages from the user's configuration and

tests/test-hiddenerror.t

@@ -39,6 +39,12 @@ Test custom error message with hash.
   (hint with hash 1ea73414a91b)
   [255]
 
+Test accessing a rev beyond the end of the repo
+  $ hg log -r 1
+  abort: hidden revision '1'!
+  (use --hidden to access hidden revisions)
+  [255]
+
 Test that basic operations like `status` don't throw an exception due
 to the wrapped context constructor.
   $ hg status