helptext: document the mechanism for extensions to report a version
Differential Revision: https://phab.mercurial-scm.org/D9448
--- a/mercurial/helptext/internals/extensions.txt Sat Nov 28 13:42:55 2020 +0100
+++ b/mercurial/helptext/internals/extensions.txt Sat Nov 28 00:25:04 2020 -0500
@@ -322,6 +322,15 @@
Older clients will print a warning that the extension requires a new version,
instead of attempting to load it.
+The extension itself can be assigned a version value through one of two module
+attributes, and will be displayed in crash reports and :hg:`version -v`::
+
+ * ``__version__`` is a plain value
+ * ``getversion`` is a no argument ``Callable`` that returns a value
+
+In both cases, the value must be either a byte string, or a list or tuple of
+numeric values which will be joined with ``.``.
+
Wrap up: what belongs where?
============================