revsymbol: stop delegating to repo.__getitem__ for unhandled symbols (API)

The only remaining cases where we were delegating unhandled symbols to
repo.__getitem__ should now be when the symbol could not be found. In
that case we just delegated to repo.__getitem__ for the error
message. Let's just copy the error message instead.

If there were any cases where we got e.g. a binary nodeid or an
integer revnum into revsymbol() (e.g. via repo.lookup()), we'd now
start raising an exception instead. That is why this is marked (API).

This affects one test case, but the new behavior seems better to me. I
can't tell if the old behavior was desired or if the test was just
there to document how it happened to work.

Differential Revision: https://phab.mercurial-scm.org/D3196

mercurial/scmutil.py

@@ -503,7 +503,7 b' def revsymbol(repo, symbol):'
             rev = repo.changelog.rev(node)
             return repo[rev]
 
-        return repo[symbol]
+        raise error.RepoLookupError(_("unknown revision '%s'") % symbol)
 
     except error.WdirUnsupported:
         return repo[None]

tests/test-pull.t

@@ -72,7 +72,7 b' not are encoded like a node:'
   [255]
   $ hg pull -r 'xxxxxxxxxxxxxxxxxx y'
   pulling from http://foo@localhost:$HGPORT/
-  abort: unknown revision '7878787878787878787878787878787878782079'!
+  abort: unknown revision 'xxxxxxxxxxxxxxxxxx y'!
   [255]
 
 Issue622: hg init && hg pull -u URL doesn't checkout default branch