maint: Replace "README--git" with "HACKING"

* README--git: Delete.
* HACKING: New file documenting how to contribute to Mcron.
* Makefile.am (EXTRA_DIST): Distribute it.

HACKING

@@ -0,0 +1,76 @@
+These notes intend to help people working on the checked-out sources.
+These requirements do not apply when building from a distribution tarball.
+
+* First Git checkout
+
+You can get a copy of the source repository like this:
+
+  $ git clone git://git.sv.gnu.org/mcron
+  $ cd mcron
+
+The next step is to get and check other files needed to build, which are
+extracted from other source packages:
+
+  $ ./bootstrap
+
+And there you are!  Just
+
+  $ ./configure
+  $ make
+
+At this point, there should be no difference between your local copy, and the
+Git master copy:
+
+  $ git diff
+
+should output no difference.
+
+Enjoy!
+
+* Submitting patches
+
+If you develop a fix or a new feature, please send it to the appropriate
+bug-reporting address as reported by the --help option of each program.  One
+way to do this is to use vc-dwim <http://www.gnu.org/software/vc-dwim/>), as
+follows.
+
+  Run the command "vc-dwim --help", copy its definition of the
+  "git-changelog-symlink-init" function into your shell, and then run this
+  function at the top-level directory of the package.
+
+  Edit the (empty) ChangeLog file that this command creates, creating a
+  properly-formatted entry according to the GNU coding standards
+  <http://www.gnu.org/prep/standards/html_node/Change-Logs.html>.
+
+  Make your changes.
+
+  Run the command "vc-dwim" and make sure its output (the diff of all your
+  changes) looks good.
+
+  Run "vc-dwim --commit".
+
+  Run the command "git format-patch --stdout -1", and email its output in,
+  using the output's subject line.
+
+-----
+
+Copyright © 2002-2017 Free Software Foundation, Inc.
+Copyright © 2017 Mathieu Lirzin <mthl@gnu.org>
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Local Variables:
+mode: outline
+fill-column: 78
+End:

Makefile.am

@@ -163,6 +163,7 @@ gen-ChangeLog:
 EXTRA_DIST = \
   bootstrap \
   build-aux/guix.scm \
+  HACKING \
   tests/init.sh \
   $(TESTS)
 

README--git

@@ -1,20 +0,0 @@
-GNU mcron --- README--git                                  -*-text-*-
-
-  Copyright (C)  2012, 2014  Dale Mellor
-  Copyright (C)  2015, 2016  Mathieu Lirzin
-
-  Copying and distribution of this file, with or without modification,
-  are permitted in any medium without royalty provided the copyright
-  notice and this notice are preserved.
-
-
-If you have pulled mcron from the GIT repository, these are the steps you will
-need to take to build it the first time:
-
-1) autoreconf -vfi
-2) ./configure --prefix={wherever}
-3) make install
-
-
-After that it should just be a simple matter of typing `make install' when you
-want to build a version with changes in it.