hook: for python hooks, also return whether an exception was raised

The hook code treats python hooks raising an exception and returning True as
the exact same. This is OK for hooks themselves, but other code that wants to
invoke external code using the same underlying code is a bit more interested in
making a distinction.

mercurial/hook.py

@@ -101,7 +101,7 b' def _pythonhook(ui, repo, name, hname, f'
         if throw:
             raise
         ui.traceback()
-        return True
+        return True, True
     finally:
         sys.stdout, sys.stderr, sys.stdin = old
         duration = time.time() - starttime
@@ -111,7 +111,7 b' def _pythonhook(ui, repo, name, hname, f'
         if throw:
             raise error.HookAbort(_('%s hook failed') % hname)
         ui.warn(_('warning: %s hook failed\n') % hname)
-    return r
+    return r, False
 
 def _exthook(ui, repo, name, cmd, args, throw):
     ui.note(_("running hook %s: %s\n") % (name, cmd))
@@ -170,7 +170,7 b' def hook(ui, repo, name, throw=False, **'
     res = runhooks(ui, repo, name, hooks, throw=throw, **args)
     r = False
     for hname, cmd in hooks:
-        r = res[hname] or r
+        r = res[hname][0] or r
     return r
 
 def runhooks(ui, repo, name, hooks, throw=False, **args):
@@ -193,7 +193,7 b' def runhooks(ui, repo, name, hooks, thro'
                     pass
 
             if callable(cmd):
-                r = _pythonhook(ui, repo, name, hname, cmd, args, throw)
+                r, raised = _pythonhook(ui, repo, name, hname, cmd, args, throw)
             elif cmd.startswith('python:'):
                 if cmd.count(':') >= 2:
                     path, cmd = cmd[7:].rsplit(':', 1)
@@ -208,11 +208,13 b' def runhooks(ui, repo, name, hooks, thro'
                     hookfn = getattr(mod, cmd)
                 else:
                     hookfn = cmd[7:].strip()
-                r = _pythonhook(ui, repo, name, hname, hookfn, args, throw)
+                r, raised = _pythonhook(ui, repo, name, hname, hookfn, args,
+                                        throw)
             else:
                 r = _exthook(ui, repo, hname, cmd, args, throw)
+                raised = False
 
-            res[hname] = r
+            res[hname] = r, raised
 
             # The stderr is fully buffered on Windows when connected to a pipe.
             # A forcible flush is required to make small stderr data in the