DOC,MAINT: Move towncrier files and fixup categories

Name all categories as singular (or adjectives). Also move the fragments
into an ``upcoming_changes`` folder to be more discoverable.

Notes that we format some things as bullet points traditionally (right now
towncrier only truly supports bullet point format, but I have a PR to fix
that).

11 files changed, 114 insertions, 47 deletions

diff --git a/doc/RELEASE_WALKTHROUGH.rst.txt b/doc/RELEASE_WALKTHROUGH.rst.txt
index 445790709..bd3e3c124 100644
--- a/doc/RELEASE_WALKTHROUGH.rst.txt
+++ b/doc/RELEASE_WALKTHROUGH.rst.txt
@@ -41,7 +41,7 @@ Finish the Release Note
 .. note:
 
   This has changed now that we use ``towncrier``. See the instructions for
-  creating the release note in ``changelog/README.rst``.
+  creating the release note in ``doc/release/upcoming_changes/README.rst``.
 
 Fill out the release note ``doc/release/1.14.5-notes.rst`` calling out
 significant changes.
diff --git a/doc/release/1.18.0-notes.rst b/doc/release/1.18.0-notes.rst
index f20d5e3fe..04bfdb7fc 100644
--- a/doc/release/1.18.0-notes.rst
+++ b/doc/release/1.18.0-notes.rst
@@ -1,43 +1,8 @@
-==========================
-NumPy 1.18.0 Release Notes
-==========================
-
-
-Highlights
-==========
-
-
-New functions
-=============
-
-
-Deprecations
-============
-
-
-Future Changes
-==============
-
-
-Expired deprecations
-====================
-
-
-Compatibility notes
-===================
-
-
-C API changes
-=============
-
-
-New Features
-============
-
-
-Improvements
-============
-
-
-Changes
-=======
+The NumPy 1.18 release is currently in developement. Please check
+the ``numpy/doc/release/upcoming_changes/`` folder for upcoming
+release notes.
+The ``numpy/doc/release/upcoming_changes/README.txt`` details how
+to add new release notes.
+
+For the work in progress release notes for the current development
+version, see the `devdocs<https://numpy.org/devdocs/release.html>`.
diff --git a/doc/release/upcoming_changes/13899.change.rst b/doc/release/upcoming_changes/13899.change.rst
new file mode 100644
index 000000000..da8277347
--- /dev/null
+++ b/doc/release/upcoming_changes/13899.change.rst
@@ -0,0 +1,4 @@
+Incorrect ``threshold`` in ``np.set_printoptions`` raises ``TypeError`` or ``ValueError``
+-----------------------------------------------------------------------------------------
+Previously an incorrect ``threshold`` raised ``ValueError``; it now raises ``TypeError``
+for non-numeric types and ``ValueError`` for ``nan`` values.
diff --git a/doc/release/upcoming_changes/14036.expired.rst b/doc/release/upcoming_changes/14036.expired.rst
new file mode 100644
index 000000000..05164aa38
--- /dev/null
+++ b/doc/release/upcoming_changes/14036.expired.rst
@@ -0,0 +1,2 @@
+* ``PyArray_As1D`` and ``PyArray_As2D`` have been removed in favor of
+  ``PyArray_AsCArray``
diff --git a/doc/release/upcoming_changes/14039.expired.rst b/doc/release/upcoming_changes/14039.expired.rst
new file mode 100644
index 000000000..effee0626
--- /dev/null
+++ b/doc/release/upcoming_changes/14039.expired.rst
@@ -0,0 +1,2 @@
+* ``np.rank`` has been removed. This was deprecated in NumPy 1.10
+  and has been replaced by ``np.ndim``.
diff --git a/doc/release/upcoming_changes/14100.expired.rst b/doc/release/upcoming_changes/14100.expired.rst
new file mode 100644
index 000000000..953922c72
--- /dev/null
+++ b/doc/release/upcoming_changes/14100.expired.rst
@@ -0,0 +1,3 @@
+* ``PyArray_FromDimsAndDataAndDescr`` has been removed, use
+  ``PyArray_NewFromDescr`` instead
+* ``PyArray_FromDims`` has been removed, use ``PyArray_SimpleNew`` instead
diff --git a/doc/release/upcoming_changes/14181.deprecation.rst b/doc/release/upcoming_changes/14181.deprecation.rst
new file mode 100644
index 000000000..9979b2246
--- /dev/null
+++ b/doc/release/upcoming_changes/14181.deprecation.rst
@@ -0,0 +1,3 @@
+Deprecate `np.alen`
+-------------------
+`np.alen` was deprecated. Use `len` instead.
diff --git a/doc/release/upcoming_changes/README.rst b/doc/release/upcoming_changes/README.rst
new file mode 100644
index 000000000..fd35850e4
--- /dev/null
+++ b/doc/release/upcoming_changes/README.rst
@@ -0,0 +1,55 @@
+:orphan:
+
+Changelog
+=========
+
+This directory contains "news fragments" which are short files that contain a
+small **ReST**-formatted text that will be added to the next what's new page.
+
+Make sure to use full sentences with correct case and punctuation, and please
+try to use Sphinx intersphinx using backticks. The fragment should have a
+header line and an underline using ``------``
+
+Each file should be named like ``<PULL REQUEST>.<TYPE>.rst``, where
+``<PULL REQUEST>`` is a pull request number, and ``<TYPE>`` is one of:
+
+* ``new_function``: New user facing functions.
+* ``deprecation``: Changes existing code to emit a DeprecationWarning.
+* ``future``: Changes existing code to emit a FutureWarning.
+* ``expired``: Removal of a deprecated part of the API.
+* ``compatibility``: A change which requires users to change code and is not
+  backwards compatible. (Not to be used for removal of deprecated features.)
+* ``c_api``: Changes in the Numpy C-API exported functions
+* ``new_feature``: New user facing features like ``kwargs``.
+* ``improvement``: Performance and edge-case changes
+* ``change``: Other changes
+* ``highlight``: Adds a highlight bullet point to use as a possibly highlight
+  of the release.
+
+Most categories shouldl be formatted as paragraphs with a heading.
+So for example: ``123.new_feature.rst`` would have the content::
+
+    ``my_new_feature`` option for `my_favorite_function`
+    ----------------------------------------------------
+    The ``my_new_feature`` option is now available for `my_favorite_function`.
+    To use it, write ``np.my_favorite_function(..., my_new_feature=True)``.
+
+``highlight`` is usually formatted as bulled points making the fragment
+``* This is a highlight``.
+
+Note the use of single-backticks to get an internal link (assuming
+``my_favorite_function`` is exported from the ``numpy`` namespace),
+and double-backticks for code.
+
+If you are unsure what pull request type to use, don't hesitate to ask in your
+PR.
+
+You can install ``towncrier`` and run ``towncrier --draft --version 1.18``
+if you want to get a preview of how your change will look in the final release
+notes.
+
+.. note::
+
+    This README was adapted from the pytest changelog readme under the terms of
+    the MIT licence.
+
diff --git a/doc/release/upcoming_changes/template.rst b/doc/release/upcoming_changes/template.rst
new file mode 100644
index 000000000..21c4d19c6
--- /dev/null
+++ b/doc/release/upcoming_changes/template.rst
@@ -0,0 +1,33 @@
+{% for section, _ in sections.items() %}
+{% set underline = underlines[0] %}{% if section %}{{section}}
+{{ underline * section|length }}{% set underline = underlines[1] %}
+
+{% endif %}
+
+{% if sections[section] %}
+{% for category, val in definitions.items() if category in sections[section]%}
+{{ definitions[category]['name'] }}
+{{ underline * definitions[category]['name']|length }}
+
+{% if definitions[category]['showcontent'] %}
+{% for text, values in sections[section][category].items() %}
+{{ text }} ({{ values|join(', ') }})
+{% endfor %}
+
+{% else %}
+- {{ sections[section][category]['']|join(', ') }}
+
+{% endif %}
+{% if sections[section][category]|length == 0 %}
+No significant changes.
+
+{% else %}
+{% endif %}
+
+{% endfor %}
+{% else %}
+No significant changes.
+
+
+{% endif %}
+{% endfor %}
diff --git a/doc/source/dev/development_workflow.rst b/doc/source/dev/development_workflow.rst
index 291b1df73..900431374 100644
--- a/doc/source/dev/development_workflow.rst
+++ b/doc/source/dev/development_workflow.rst
@@ -203,8 +203,9 @@ function, you should
   a description of and a motivation for your changes. This may generate
   changes and feedback. It might be prudent to start with this step if your
   change may be controversial.
-- add a release note to the ``changelog`` directory, following the instructions
-  and format in the ``changelog/README.rst`` file.
+- add a release note to the ``doc/release/upcoming_changes/`` directory,
+  following the instructions and format in the
+  ``doc/release/upcoming_changes/README.rst`` file.
 
 .. _rebasing-on-master:
 
diff --git a/doc/source/release.rst b/doc/source/release.rst
index 8dfb8db1d..f8d83726f 100644
--- a/doc/source/release.rst
+++ b/doc/source/release.rst
@@ -2,7 +2,6 @@
 Release Notes
 *************
 
-.. include:: ../release/1.18.0-notes.rst
 .. include:: ../release/1.17.0-notes.rst
 .. include:: ../release/1.16.4-notes.rst
 .. include:: ../release/1.16.3-notes.rst