Drop support for Emacs 27

Transient no longer supports Emacs 27, which is the primary reason for this
change.

Author: bbatsov

.github/workflows/test.yml

@@ -24,8 +24,8 @@ jobs:
         # Test all Emacs versions on Ubuntu.
         os: [ubuntu-latest]
         # TODO: reenable snapshot once this is fixed https://app.circleci.com/pipelines/github/clojure-emacs/cider/2931/workflows/b7284759-c6d1-44dd-bbfc-e71709e3f62f/jobs/17699
-        # emacs_version: ['27.2', '28.2', '29.3', '30.1', 'snapshot']
-        emacs_version: ['27.2', '28.2', '29.3', '30.1']
+        # emacs_version: ['28.2', '29.3', '30.1', 'snapshot']
+        emacs_version: ['28.2', '29.3', '30.1']
         java_version: ['21']
         include:
           # For other OSes, test only the latest stable Emacs version.

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Changes
 
 - [#3854](https://github.com/clojure-emacs/cider/pull/3854): Use buttons for items in `cider-ns-browser` to allow clicking and evil's `RET` to navigate.
+- Drop support for Emacs 27.
 
 ### Bugs fixed
 

cider.el

@@ -16,7 +16,7 @@
 ;;
 ;; Version: 1.21.0-snapshot
 ;; Package-Requires: (
-;;     (emacs "27")
+;;     (emacs "28")
 ;;     (clojure-mode "5.19")
 ;;     (parseedn "1.2.1")
 ;;     (queue "0.2")

doc/modules/ROOT/pages/about/compatibility.adoc

@@ -2,7 +2,7 @@
 
 == Emacs
 
-CIDER supports Emacs 27.1+. More generally we try to support the last 3 major Emacs releases
+CIDER supports Emacs 28.1+. More generally we try to support the last 3 major Emacs releases
 when that's feasible and doesn't add a lot of maintenance overhead.
 
 NOTE: We pay special attention to supporting whatever Emacs is bundled with the current stable Debian
@@ -103,6 +103,13 @@ Below you can find the official compatibility matrix for CIDER.
 | 8
 | 1.10
 
+| 1.21
+| 28.1
+| 1.0
+| 0.58
+| 8
+| 1.10
+
 |===
 
 TIP: You can also check the requirements of a particular CIDER version by inspecting

doc/modules/ROOT/pages/basics/installation.adoc

@@ -14,7 +14,7 @@ release. If you're new to Emacs you might want to go through
 https://www.gnu.org/software/emacs/tour/index.html[the guided tour of Emacs]
 and the built-in tutorial (just press kbd:[C-h t]).
 
-CIDER officially supports Emacs 27.1+, Java 8+, and Clojure(Script) 1.10+. If
+CIDER officially supports Emacs 28.1+, Java 8+, and Clojure(Script) 1.10+. If
 you need to work with earlier versions, check
 xref:about/compatibility.adoc#compatibility-matrix[compatibility matrix].