activate Nix CI and fix boilerplate

.github/workflows/nix-action.yml

@@ -5,7 +5,7 @@ name: Nix CI
 on:
   push:
     branches:
-      - master
+      - v8.15
   pull_request:
     paths:
     - .github/workflows/**
@@ -17,7 +17,7 @@ jobs:
     strategy:
       matrix:
         overrides:
-          - 'coq = "master"'
+          - 'coq = "8.15"'
       fail-fast: false
     steps:
       - name: Determine which commit to test

README.md

@@ -41,7 +41,7 @@ algorithm in Coq.
 - Coq-community maintainer(s):
   - Karl Palmskog ([**@palmskog**](https://github.com/palmskog))
 - License: [GNU Lesser General Public License v2.1 or later](LICENSE)
-- Compatible Coq versions: Coq master (use the corresponding branch or release for other Coq versions)
+- Compatible Coq versions: Coq 8.15 (use the corresponding branch or release for other Coq versions)
 - Additional dependencies: none
 - Coq namespace: `Stalmarck.Algorithm`
 - Related publication(s):

meta.yml

@@ -40,7 +40,7 @@ license:
   identifier: LGPL-2.1-or-later
 
 supported_coq_versions:
-  text: Coq master (use the corresponding branch or release for other Coq versions)
+  text: Coq 8.15 (use the corresponding branch or release for other Coq versions)
   opam: '{>= "8.15" & < "8.16~"}'
 
 tested_coq_nix_versions: