windows: read all global config files, not just the first (issue4491) (BC)

On windows, hgrc.d/*.rc would not be read if mercurial.ini was found. That was
far from obvious from the documentation and different from the behavior on
posix systems.

As a consequence of this, TortoiseHg cacert configuration placed in hgrc.d
would not be read if an old global mercurial.ini still existed.

"hg config -g" could also crash when no global configuration files could be
found.

Instead, make windows behave like posix and read all global configuration
files.

The documentation was in a way right that individual config settings in the
global Mercurial.ini would override settings from for example .hgrc.d\*.rc, but
only because the .d files not would be read at all if a Mercurial.ini was
found. The ordering in the documentation is thus changed to match the code.

mercurial/help/config.txt

@@ -62,9 +62,9 b' ones.'
   - ``%USERPROFILE%\Mercurial.ini`` (per-user)
   - ``%HOME%\.hgrc`` (per-user)
   - ``%HOME%\Mercurial.ini`` (per-user)
-  - ``<install-dir>\Mercurial.ini`` (per-installation)
+  - ``HKEY_LOCAL_MACHINE\SOFTWARE\Mercurial`` (per-installation)
   - ``<install-dir>\hgrc.d\*.rc`` (per-installation)
-  - ``HKEY_LOCAL_MACHINE\SOFTWARE\Mercurial`` (per-installation)
+  - ``<install-dir>\Mercurial.ini`` (per-installation)
   - ``<internal>/default.d/*.rc`` (defaults)
 
   .. note::

mercurial/scmwindows.py

@@ -9,16 +9,13 b' def systemrcpath():'
     filename = util.executablepath()
     # Use mercurial.ini found in directory with hg.exe
     progrc = os.path.join(os.path.dirname(filename), 'mercurial.ini')
-    if os.path.isfile(progrc):
-        rcpath.append(progrc)
-        return rcpath
+    rcpath.append(progrc)
     # Use hgrc.d found in directory with hg.exe
     progrcd = os.path.join(os.path.dirname(filename), 'hgrc.d')
     if os.path.isdir(progrcd):
         for f, kind in osutil.listdir(progrcd):
             if f.endswith('.rc'):
                 rcpath.append(os.path.join(progrcd, f))
-        return rcpath
     # else look for a system rcpath in the registry
     value = util.lookupreg('SOFTWARE\\Mercurial', None,
                            _winreg.HKEY_LOCAL_MACHINE)