README.md: Remove instructions for patching into Sage < 9.1

README.md

@@ -5,17 +5,12 @@
 
 `CoinBackend` has previously been available as part of the [SageMath](http://www.sagemath.org/) source tree,
 from which it is built as an "optional extension" when the `cbc` Sage package is installed.
+However, it has not been available in binary distributions.
 
-However, it is not available in binary distributions such as:
-- the Sage binary distribution (which does not package any optional packages),
-- homebrew (which just uses the Sage binary distribution),
-- Ubuntu (bionic 18.04LTS and several newer versions ship versions of SageMath, with various optional packages including CBC, but not the optional extension module CoinBackend),
-- conda-forge (which ships SageMath and CBC but not the optional extension).
-- Fedora
+The present standalone Python package `sage-numerical-backends-coin` has been created from the SageMath sources, version 9.0.beta10; the in-tree version of `CoinBackend` has been removed in Sage ticket https://trac.sagemath.org/ticket/28175.  SageMath 9.1 and later makes the package available as an optional Sage package (SPKG).
 
-The present standalone Python package `sage-numerical-backends-coin` has been created from the SageMath sources, version 9.0.beta10.  It can be installed on top of various Sage installations using pip, including all of the above, including older versions of Sage such as 8.1 (as shipped by Ubuntu bionic 18.04LTS).
-
-Sage ticket https://trac.sagemath.org/ticket/28175 uses this package to remove the in-tree version of `CoinBackend`.
+The current version of this package can also be installed on top of various Sage installations using pip.
+(Your installation of Sage must be based on Python 3; if your SageMath is version 9.2 or newer, it is.)
 
 ## Installation
 
@@ -29,50 +24,24 @@ This package finds the CBC installation by means of ``pkgconfig``.
 
 Install this package from PyPI using
 
-    $ sage -python -m pip install sage-numerical-backends-coin
+    $ sage -pip install sage-numerical-backends-coin
 
 or from GitHub using
 
-    $ sage -python -m pip install git+https://github.com/sagemath/sage-numerical-backends-coin
+    $ sage -pip install git+https://github.com/sagemath/sage-numerical-backends-coin
 
 (See [`.github/workflows/build.yml`](.github/workflows/build.yml) for details about package prerequisites on various systems.)
 
 ## Using this package
 
-To obtain a solver (backend) instance:
-
-    sage: from sage_numerical_backends_coin.coin_backend import CoinBackend
-    sage: CoinBackend()
-    <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7fb72c2c7528>
-
-Equivalently:
-
-    sage: from sage_numerical_backends_coin.coin_backend import CoinBackend
-    sage: from sage.numerical.backends.generic_backend import get_solver
-    sage: get_solver(solver=CoinBackend)
-    <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7fe21ffbe2b8>
-
-To use this solver (backend) with [`MixedIntegerLinearProgram`](http://doc.sagemath.org/html/en/reference/numerical/sage/numerical/mip.html):
-
-    sage: from sage_numerical_backends_coin.coin_backend import CoinBackend
-    sage: M = MixedIntegerLinearProgram(solver=CoinBackend)
-    sage: M.get_backend()
-    <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7fb72c2c7868>
-
-To make it available as the solver named `'Coin'`, we need to make the new module
-known as `sage.numerical.backends.coin_backend` (note dots, not underscores), using
-the following commands:
-
-    sage: import sage_numerical_backends_coin.coin_backend as coin_backend, sage.numerical.backends as backends, sys
-    sage: sys.modules['sage.numerical.backends.coin_backend'] = backends.coin_backend = coin_backend
+After a successful installation, Sage will automatically make this new backend
+the default MIP solver.
 
-If these commands are executed in a Sage session before any `MixedIntegerLinearProgram` is created, then
-the new `'Coin'` solver wins over the `'GLPK'` solver in the selection of the default MIP backend.
 To select the `'Coin'` solver explicitly as the default MIP backend, additionally use the following command.
 
     sage: default_mip_solver('Coin')
 
-To make these settings permanent, add the above 2 + 1 commands to your `~/.sage/init.sage` file.
+To make these settings permanent, add this command to your `~/.sage/init.sage` file.
 Note that this setting will not affect doctesting (`sage -t`) because this file is ignored in doctesting mode.
 
 ## Running doctests
@@ -97,20 +66,3 @@ If you have `docker` installed, more tests can be run:
     $ tox -e docker-sage_binary-cbc_coinbrew
 
 See `tox.ini` for the available options.
-
-## Overriding the default solver by patching the Sage installation
-
-Another method is to patch the module in permanently to the sage installation (at your own risk).
-This method will affect doctesting.
-
-    $ sage -c 'import os; import sage.numerical.backends as dm; import sage_numerical_backends_coin.coin_backend as sm; s = sm.__file__; f = os.path.basename(s); d = os.path.join(dm.__path__[0], f); (os.path.exists(d) or os.path.lexists(d)) and os.remove(d); os.symlink(s, d);'
-
-Or use the script [`patch_into_sage_module.py`](patch_into_sage_module.py) in the source distribution that does the same:
-
-    $ sage -c 'load("patch_into_sage_module.py")'
-    Success: Patched in the module as sage.numerical.backends.coin_backend
-
-Verify with [`check_get_solver_with_name.py`](check_get_solver_with_name.py) that the patching script has worked:
-
-    $ sage -c 'load("check_get_solver_with_name.py")'
-    Success: get_solver(solver='coin') gives <sage_numerical_backends_coin.coin_backend.CoinBackend object at 0x7f8f20218528>