Update devdocs

docs/Makefile

@@ -18,9 +18,10 @@ allapi:
 	rm -rf ./details/api
 	sphinx-apidoc -Mfe -o ./details/api ../lib/ncdata
 
+# N.B. when no changelog entries pending, *don't* add a release section.
+#  - this gives a "clean" changelog when building a release version.
 towncrier:
-	if [ -e changelog_fragments/*.rst ]; then towncrier build --yes; fi
-
+	if [ "$$(ls changelog_fragments | grep "\.rst")" != "" ]; then towncrier build --yes; fi
 
 # Tweaked "make html", which restores the changelog state after docs build.
 html-keeplog: html

docs/changelog_fragments/173.dev.rst

@@ -0,0 +1 @@
+Fix xarray 2025.09.1 problem.

docs/changelog_fragments/174.doc.rst

@@ -0,0 +1 @@
+Document how to create a developer installation.

docs/changelog_fragments/175.dev.rst

@@ -0,0 +1,2 @@
+Test against given Python versions : currently 3.12 and 3.13.
+**Not** python 3.14, for now, due to emerging problems with dependencies (notably Iris).

docs/details/developer_notes.rst

@@ -19,7 +19,7 @@ with a ``towncrier`` command-line command:
     * "feat": user features
     * "doc": documentation changes
     * "bug": bug fixes
-    * "def": general developer-relevant changes
+    * "dev": general developer-relevant changes
     * "misc": miscellaneous
 
   (For reference, these categories are configured in ``pyproject.toml``).
@@ -29,6 +29,19 @@ with a ``towncrier`` command-line command:
 * N.B. for this to work well, every change should be identified with a matching github issue.
   If there are multiple associated PRs, they should all be linked to the issue.
 
+.. _developer_install:
+
+Developer Installation
+----------------------
+For an editable installation, make a Python environment containing at least **numpy,
+netCDF4, dask and pip**.  It is also highly recommended to get
+`towncrier <https://github.com/twisted/towncrier>`_ and
+`pre-commit <https://github.com/pre-commit/pre-commit>`_.
+(and enable pre-commit with ``$ pre-commit install``).
+
+Then, cd to your checkout, and ``$ pip install -e .``.
+This should result in an editable development installation.
+
 
 Documentation build
 -------------------
@@ -83,7 +96,7 @@ Release actions
 
     #. create a new env with test dependencies
 
-       * ``$ conda create -n ncdtmp python=3.11 iris xarray filelock requests pytest pip``
+       * ``$ conda create -n ncdtmp python=3.13 iris xarray filelock requests pytest pip``
        * ( N.B. 'filelock' and 'requests' are *test dependencies* of iris )
 
     #. install the new package with

docs/userdocs/getting_started/installation.rst

@@ -29,3 +29,8 @@ Check install
     <NcData: <'no-name'>
     >
 
+
+Developer Installation
+----------------------
+To work on changes to the ncdata code, you will need an "editable installation".
+See : :ref:`developer_install`.