docs: Update outdated code.orgmode.org links

* CONTRIBUTE, docs/org-manual.org, docs/ORG-NEWS: Replace mentions
of https://code.orgmode.org with references to the new repository
on Savannah (https://git.savannah.gnu.org).

CONTRIBUTE

@@ -5,30 +5,26 @@ development.
 
 * Main contribution rules
 
-1. The master git repository is hosted publicly at [[https://orgmode.org][orgmode.org]].
+1. The master git repository is hosted publicly on [[https://savannah.gnu.org][savannah.gnu.org]].
 
-   Anyone can get a clone of the current repository state using the
-   command
+   : git clone https://git.savannah.gnu.org/git/emacs/org-mode.git
 
-   : git clone https://code.orgmode.org/bzg/org-mode.git
+   This is sufficient to start hacking and to produce patches that can
+   easily and consistently be applied to the main repository.
 
-   Having a clone is sufficient to start hacking and to produce
-   patches that can easily and consistently be applied to the main
-   repository.
-
-2. People who are interested in participating to the Org mode
-   development can do so by sending patches to this address:
+2. People who want to participate to the Org mode development can send
+   patches to this address:
 
    : emacs-orgmode@gnu.org
 
-3. An interested developer can also request push access to the central
-   repository by creating an account on code.orgmode.org and by
-   sending her/his user info to the maintainer.
+3. If you are a regular contributor, you can request push access to
+   the repository by creating an account on [[https://savannah.gnu.org/account/register.php][savannah.gnu.org]] and by
+   [[https://savannah.gnu.org/git/?group=emacs][joining the Emacs group]].
+   
+   After you have been added as a user with push privileges, you can
+   clone the repository like this:
 
-   After you have been added as a user with push privileges, clone the
-   repository through ssh using
-
-   : git clone git@code.orgmode.org:bzg/org-mode.git
+   : git clone git://git.savannah.gnu.org/emacs/org-mode.git
 
    By requesting push access, you acknowledge that you have read and
    agreed with the following rules:
@@ -40,14 +36,13 @@ development.
      applies are:
 
      - all *.el files in the lisp directory of the repository
-     - org.texi, orgcard.tex in the doc directory
-     - the corresponding ChangeLog files
+     - org.texi, orgcard.tex in the doc/ directory
 
    - Before making any significant changes, please explain and discuss
-     them on the mailing list [[mailto:emacs-orgmode@gnu.org][emacs-orgmode@gnu.org]].  
+     them on the mailing list [[mailto:emacs-orgmode@gnu.org][emacs-orgmode@gnu.org]].
 
      This does obviously not apply to people who are maintaining their
-     own contributions to Org mode. Please, just use the new mechanism
+     own contributions to Org mode.  Please just use the new mechanism
      to make sure all changes end up in the right place.
 
      We value a nice tone in our discussions: please check and respect
@@ -58,9 +53,8 @@ development.
      `CONTRIBUTE' file in the main Emacs repository.
 
    - Among other things, Org mode is widely appreciated because of its
-     simplicity, cleanness and consistency.  We should try hard to
-     preserve this and ask everyone to keep this in mind when
-     proposing changes.
+     simplicity, cleanness and consistency.  We should try to preserve
+     them and ask everyone to keep this in mind when posting changes.
 
 * The contrib/ directory
 

doc/org-manual.org

@@ -141,7 +141,7 @@ You can clone Org's repository and install Org like this:
 
 #+begin_example
 $ cd ~/src/
-$ git clone https://code.orgmode.org/bzg/org-mode.git
+$ git clone https://git.savannah.gnu.org/git/emacs/org-mode.git
 $ cd org-mode/
 $ make autoloads
 #+end_example

etc/ORG-NEWS

@@ -3,7 +3,7 @@ ORG NEWS -- history of user-visible changes.   -*- mode: org; coding: utf-8 -*-
 #+STARTUP: overview
 
 #+LINK: doc https://orgmode.org/worg/doc.html#%s
-#+LINK: git https://code.orgmode.org/bzg/org-mode/commit/%s
+#+LINK: git https://git.savannah.gnu.org/cgit/emacs/org-mode.git/commit/?id=%s
 
 Copyright (C) 2012-2021 Free Software Foundation, Inc.
 See the end of the file for license conditions.
@@ -354,7 +354,7 @@ source buffers are displayed by modifying ~display-buffer-alist~ or
 *** New option ~org-archive-subtree-save-file-p~
 
 Archiving a subtree used to always save the target archive buffer.
-Commit [[https://code.orgmode.org/bzg/org-mode/commit/b186d1d7][b186d1d7]] changed this behavior by always not saving the target
+Commit [[git::b186d1d7][b186d1d7]] changed this behavior by always not saving the target
 buffer, because batch archiving from agenda could take too much time.
 
 This new option ~org-archive-subtree-save-file-p~ defaults to the
@@ -388,7 +388,7 @@ In all Babel libraries, the absence of a ~:results~ header should
 produce the same result than setting ~:results value~, unless there is
 an option to explicitly create an exception.
 
-See [[https://orgmode.org/list/CA+A2iZaziAfMeGpBqL6qGrzrWEVvLvC0DUw++T4gCF3NGuW-DQ@mail.gmail.com/][this thread]] for more context.
+See [[https://list.orgmode.org/CA+A2iZaziAfMeGpBqL6qGrzrWEVvLvC0DUw++T4gCF3NGuW-DQ@mail.gmail.com/][this thread]] for more context.
 
 *** New option in ~org-attach-store-link-p~
 
@@ -5131,7 +5131,7 @@ that Calc formulas can operate on them.
 
     The new system has a technically cleaner implementation and more
     possibilities for capturing different types of data.  See
-    [[https://orgmode.org/list/C46F10DC-DE51-43D4-AFFE-F71E440D1E1F@gmail.com][Carsten's announcement]] for more details.
+    [[https://list.orgmode.org/C46F10DC-DE51-43D4-AFFE-F71E440D1E1F@gmail.com][Carsten's announcement]] for more details.
 
     To switch over to the new system:
 
@@ -5262,7 +5262,7 @@ that Calc formulas can operate on them.
 
 **** Modified link escaping
 
-     David Maus worked on `org-link-escape'.  See [[https://orgmode.org/list/87k4gysacq.wl%dmaus@ictsoc.de][his message]]:
+     David Maus worked on `org-link-escape'.  See [[https://list.orgmode.org/87k4gysacq.wl%dmaus@ictsoc.de][his message]]:
 
      : Percent escaping is used in Org mode to escape certain characters
      : in links that would either break the parser (e.g. square brackets