hook: fix full path imports on Windows (issue1779)

Bottom portion fixes full path imports on source installs on Windows.
The top portion further fixes full path imports on binary installs.

Initial patch by Roman V. Kiseliov

mercurial/hook.py

@@ -27,6 +27,13 b' def _pythonhook(ui, repo, name, hname, f'
             raise util.Abort(_('%s hook is invalid ("%s" not in '
                                'a module)') % (hname, funcname))
         modname = funcname[:d]
+        oldpaths = sys.path[:]
+        if hasattr(sys, "frozen"):
+            # binary installs require sys.path manipulation
+            path, name = os.path.split(modname)
+            if path and name:
+                sys.path.append(path)
+                modname = name
         try:
             obj = __import__(modname)
         except ImportError:
@@ -37,6 +44,7 b' def _pythonhook(ui, repo, name, hname, f'
                 raise util.Abort(_('%s hook is invalid '
                                    '(import of "%s" failed)') %
                                  (hname, modname))
+        sys.path = oldpaths
         try:
             for p in funcname.split('.')[1:]:
                 obj = getattr(obj, p)
@@ -110,9 +118,9 b' def hook(ui, repo, name, throw=False, **'
             if hasattr(cmd, '__call__'):
                 r = _pythonhook(ui, repo, name, hname, cmd, args, throw) or r
             elif cmd.startswith('python:'):
-                if cmd.count(':') == 2:
-                    path, cmd = cmd[7:].split(':')
-                    mod = extensions.loadpath(path, 'hgkook.%s' % hname)
+                if cmd.count(':') >= 2:
+                    path, cmd = cmd[7:].rsplit(':', 1)
+                    mod = extensions.loadpath(path, 'hghook.%s' % hname)
                     hookfn = getattr(mod, cmd)
                 else:
                     hookfn = cmd[7:].strip()