hooks: clarify in UI and documentation how the hook control essentially is Mercurial only

The Git hook model doesn't directly allow multiple hooks of the same kind.

docs/setup.rst

@@ -338,15 +338,19 b' the supported syntax in ``issue_pat``, `'
 Hook management
 ---------------
 
-Hooks can be managed in similar way to that used in ``.hgrc`` files.
+Custom Mercurial hooks can be managed in a similar way to that used in ``.hgrc`` files.
 To manage hooks, choose *Admin > Settings > Hooks*.
 
-The built-in hooks cannot be modified, though they can be enabled or disabled in the *VCS* section.
-
 To add another custom hook simply fill in the first textbox with
 ``<name>.<hook_type>`` and the second with the hook path. Example hooks
 can be found in ``kallithea.lib.hooks``.
 
+Kallithea will also use some hooks internally. They cannot be modified, but
+some of them can be enabled or disabled in the *VCS* section.
+
+Kallithea has no support for custom Git hooks. Kallithea will install and use
+Git hooks internally, and they might collide with manually installed hooks.
+
 
 Changing default encoding
 -------------------------

docs/upgrade.rst

@@ -225,8 +225,8 b' clear out your log file so that new erro'
     upgrade.
 
 
-10. Update Git repository hooks
--------------------------------
+10. Reinstall internal Git repository hooks
+-------------------------------------------
 
 It is possible that an upgrade involves changes to the Git hooks installed by
 Kallithea. As these hooks are created inside the repositories on the server

docs/usage/troubleshooting.rst

@@ -43,12 +43,18 b' Troubleshooting'
 |
 
 :Q: **How can I use hooks in Kallithea?**
-:A: It's easy if they are Python hooks: just use advanced link in
-    hooks section in Admin panel, that works only for Mercurial. If
-    you want to use Git hooks, just install th proper one in the repository,
-    e.g., create a file `/gitrepo/hooks/pre-receive`. You can also use
-    Kallithea-extensions to connect to callback hooks, for both Git
-    and Mercurial.
+:A: If using Mercurial, use *Admin > Settings > Hooks* to install
+    global hooks. Inside the hooks, you can use the current working directory to
+    control different behaviour for different repositories.
+
+    If using Git, install the hooks manually in each repository, for example by
+    creating a file ``gitrepo/hooks/pre-receive``.
+    Note that Kallithea uses the ``post-receive`` hook internally.
+    Kallithea will not work properly if another post-receive hook is installed instead.
+    You might also accidentally overwrite your own post-receive hook with the Kallithea hook.
+
+    You can also use Kallithea-extensions to connect to callback hooks,
+    for both Git and Mercurial.
 
 |
 

kallithea/templates/admin/settings/settings_hooks.html

@@ -2,7 +2,7 b''
 ${h.form(url('admin_settings_hooks'), method='post')}
 <div class="form">
       <div class="form-group">
-        <h4>${_('Custom Hooks')}</h4>
+        <h4>${_('Custom Global Mercurial Hooks')}</h4>
         <span class="help-block">${_('Hooks can be used to trigger actions on certain events such as push / pull. They can trigger Python functions or external applications.')}</span>
         %for hook in c.custom_hooks:
             <div class="form-group form-inline" id="${'id%s' % hook.ui_id }">
@@ -37,6 +37,15 b''
       </div>
 </div>
 ${h.end_form()}
+
+<div class="form">
+      <div class="form-group">
+      <h4>${_('Git Hooks')}</h4>
+      <span class="help-block">${h.HTML(_('Kallithea has no support for custom Git hooks. Kallithea will use Git post-receive hooks internally. Installation of these hooks is managed in %s.')) % (h.literal('''<a href="%s">%s</a>''') % (h.url('admin_settings_mapping'), _('Remap and Rescan')))}</span>
+</div>
+
+% else:
+      <h4>${_('Custom Hooks are not enabled')}</h4>
 % endif
 
 <script>

kallithea/templates/admin/settings/settings_vcs.html

@@ -1,7 +1,7 b''
 ${h.form(url('admin_settings'), method='post')}
     <div class="form">
             <div class="form-group">
-                <label class="control-label">${_('Hooks')}:</label>
+                <label class="control-label">${_('Mercurial Push Hooks')}:</label>
                 <div>
                     <div class="checkbox">
                         <label>