ci: fix doxygen generation not running

Also took the opportunity to add some sensible filters to the main ci script.

.github/workflows/ci.yaml

@@ -1,6 +1,30 @@
 name: ci
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - '**.h'
+      - '**.hpp'
+      - '**.cpp'
+      - '**.inl'
+      - '**.py'
+      - '**/meson.build'
+  pull_request:
+    branches:
+      - master
+    paths:
+      - '**.h'
+      - '**.hpp'
+      - '**.cpp'
+      - '**.inl'
+      - '**.py'
+      - '**/meson.build'
+  workflow_dispatch:
+    branches:
+      - master
+
 
 # This ensures that jobs get canceled when force-pushing
 concurrency:

.github/workflows/gh-pages.yaml

@@ -2,8 +2,16 @@ name: gh-pages
 
 on:
   push:
-    branches: master
+    branches:
-    paths: docs/**
+      - master
+    paths:
+      - '**.h'
+      - '**.hpp'
+      - '**.dox'
+      - 'docs/**'
+  workflow_dispatch:
+    branches:
+      - master
 
 jobs:
   gh-pages:
@@ -21,7 +29,7 @@ jobs:
       - name: Install dependencies
         run: |
           apt-get -y update
-          apt-get -y install --no-install-recommends python3-pip doxygen
+          apt-get -y install --no-install-recommends python3-pip doxygen git
           pip3 install --upgrade --requirement tools/requirements.txt
 
       - name: Generate docs