btrfs-progs: ci: build html manual page previews if source changed

Similar to the manual page on terminal preview, also do the html output
that will be on the RTD page. Due to the way how it's displayed in the
CI action summary the CSS is missing and there are some visual
artifacts, e.g. in the option lists or special characters.

Issue: #824
Signed-off-by: David Sterba <dsterba@suse.com>

.github/workflows/devel.yml

@@ -28,7 +28,17 @@ jobs:
         run: ./autogen.sh && CC=${{ matrix.compiler }} ./configure
       - name: Documentation
         run: make V=1 -C Documentation
-      - name: Generate manual pages preview
+      - name: Generate manual pages preview (html)
+        if: ${{ matrix.compiler == 'gcc' }}
+        env:
+          ALL_CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}
+        run: |
+          for file in ${ALL_CHANGED_FILES}; do
+            echo "$file was changed, generate preview to summary"
+            Documentation/html-preview.sh "$file" >> $GITHUB_STEP_SUMMARY
+          done
+      - run: echo '<hr>' >> $GITHUB_STEP_SUMMARY
+      - name: Generate manual pages preview (man)
         if: ${{ matrix.compiler == 'gcc' }}
         env:
           ALL_CHANGED_FILES: ${{ steps.changed-files.outputs.all_changed_files }}

Documentation/html-preview.sh

@@ -0,0 +1,41 @@
+#!/bin/sh
+# Generate manual page preview as rendered by 'make html', removed some styling
+# so there can be visual artifacts, usable for CI summary
+
+if ! [ -f "$1" ]; then
+	exit 0
+fi
+
+prefix=Documentation/
+here=$(pwd)
+
+if [ "$(basename \"$here\")" = 'Documentation' ]; then
+	prefix=
+fi
+
+fn="$1"
+bn=$(basename "$fn" .rst)
+html=$(find "${prefix}"_build/html -name "$bn".'html')
+
+if ! [ -f "$html" ]; then
+	#echo "ERROR: cannot find html page '$html' from bn $bn fn $fn <br/>"
+	exit 0
+fi
+
+cat << EOF
+<details>
+<summary>$fn</summary>
+
+EOF
+
+# Up to <div itemprop="articleBody">, before that there's left bar navigation
+
+cat "$html" | sed -e 's/^\s\+//' | awk '
+/^<div itemprop=.articleBody.>/ { doit=1; next; }
+/^<\/body>/ { doit=0; next; }
+doit==1 { print; }'
+
+cat << EOF
+
+</details>
+EOF