traceback: allow providing a local support contact point

The extensions blaming code is fine for casual users but pretty terrible for
corporate environments that can deploy a large amount of extensions to
unsuspecting users. Reports will likely blame a random "innocent" extension (in
our case crecord) and the hint in the message will triggers endless debug
attempts from the user.

We introduce a "ui.supportcontact" option that allow such big company to redirect
their users to their own support desk. This disables all extensions blaming and
just point people to the local support in all cases.

mercurial/dispatch.py

@@ -335,7 +335,7 b' def _runcatch(req):'
         compare = myver.split('+')[0]
         ct = tuplever(compare)
         worst = None, ct, ''
-        if True:
+        if ui.config('ui', 'supportcontact', None) is None:
             for name, mod in extensions.extensions():
                 testedwith = getattr(mod, 'testedwith', '')
                 report = getattr(mod, 'buglink', _('the extension author.'))
@@ -367,9 +367,11 b' def _runcatch(req):'
                          '** If that fixes the bug please report it to %s\n')
                        % (name, testedwith, name, report))
         else:
+            bugtracker = ui.config('ui', 'supportcontact', None)
+            if bugtracker is None:
+                bugtracker = _("http://mercurial.selenic.com/wiki/BugTracker")
             warning = (_("** unknown exception encountered, "
-                         "please report by visiting\n") +
-                       _("** http://mercurial.selenic.com/wiki/BugTracker\n"))
+                         "please report by visiting\n** ") + bugtracker + '\n')
         warning += ((_("** Python %s\n") % sys.version.replace('\n', '')) +
                     (_("** Mercurial Distributed SCM (version %s)\n") % myver) +
                     (_("** Extensions loaded: %s\n") %

mercurial/help/config.txt

@@ -1511,6 +1511,11 b' User interface controls.'
 ``style``
     Name of style to use for command output.
 
+``supportcontact``
+    Location pointed at in Mercurial traceback for reporting crash. Use this if
+    you are a large organisation with it's own Mercurial deployement process and
+    crash reports should be addressed to your internal support.
+
 ``timeout``
     The timeout used when a lock is held (in seconds), a negative value
     means no timeout. (default: 600)

tests/test-extension.t

@@ -943,6 +943,15 b' Older extension is tested with current v'
   ** Mercurial Distributed SCM (version 1.9.3)
   ** Extensions loaded: throw, older
 
+Ability to point to a different point
+  $ hg --config extensions.throw=throw.py --config extensions.older=older.py \
+  >   --config ui.supportcontact='Your Local Goat Lenders' throw 2>&1 | egrep '^\*\*'
+  ** unknown exception encountered, please report by visiting
+  ** Your Local Goat Lenders
+  ** Python * (glob)
+  ** Mercurial Distributed SCM (*) (glob)
+  ** Extensions loaded: throw, older
+
 Declare the version as supporting this hg version, show regular bts link:
   $ hgver=`$PYTHON -c 'from mercurial import util; print util.version().split("+")[0]'`
   $ echo 'testedwith = """'"$hgver"'"""' >> throw.py