Support metadata for galleries

Name and cover can now be changed.

boop.py

 import os
 import shutil
 import re
+import yaml
 
 from operator import itemgetter
 
         photos = list(list_photos_in(gallery_dir))
         if len(photos) == 0:
             continue
-
         photos.sort(key=itemgetter("name"))
-        cover_index = (len(gallery_dir.name) + 42) % len(photos)
+
+        metadata = {}
+        metadata_path = os.path.join(gallery_dir.path, "metadata.yml")
+        if os.path.exists(metadata_path):
+            with open(metadata_path, "r") as metadata_file:
+                metadata = yaml.load(metadata_file)
+
+        # Try to get cover from metadata, if it doesn't exist, take one by
+        # default.
+        cover_photo = None
+        cover_name = metadata.get("cover")
+        if cover_name:
+            cover_photo = find_photo(photos, cover_name)
+        if cover_photo is None:
+            cover_index = (len(gallery_dir.name) + 42) % len(photos)
+            cover_photo = photos[cover_index]
+
         gallery = {
-            "name": gallery_dir.name,
+            "name": metadata.get("name", gallery_dir.name),
             "path": gallery_dir.path,
             "output_path": gallery_dir.name,
             "url": f"{gallery_dir.name}.html",
             "num_photos": len(photos),
             "photos": photos,
-            "cover_photo": photos[cover_index],
+            "cover_photo": cover_photo,
         }
         yield gallery
 
 
+def find_photo(photos, photo_name):
+    for photo in photos:
+        if photo["name"] == photo_name:
+            return photo
+    else:
+        return None
+
+
 def list_photos_in(gallery_dir):
     photo_files = [
         f for f in os.scandir(gallery_dir) if re.match(".+\.jpg", f.name, re.I)

photos/2013_08_2013_12_Trondheim/metadata.yml

+---
+name: "3. Trondheim"
+cover: "DSC00179.jpg"

photos/2013_08_Bergen/metadata.yml

+---
+name: "1. Bergen"
+cover: "DSC00100.jpg"

photos/2013_08_hiking_five_fifty_two/metadata.yml

+---
+name: "2. Hiking five fifty-two"
+cover: "DSC00133.jpg"

photos/2013_09_5_hours_walk/metadata.yml

+---
+name: "4. 5 hours walk"
+cover: "DSC00302.jpg"

photos/2013_12_Prague/metadata.yml

+---
+name: "5. Prague"
+cover: "DSC00425.jpg"

photos/2015_03-2015_04-Tour_de_France/metadata.yml

+---
+name: "6. Tour de France"
+cover: "07_Blois_02542.jpg"

photos/2015_05-2015_06_Tour_Europe/metadata.yml

+---
+name: "7. Tour d’Europe"
+cover: "06_Tchou_tchou_03411.jpg"

photos/2017-05_2017-06_Royaume_Uni/metadata.yml

+---
+name: "8. Royaume-Uni"
+cover: "DSC03695.JPG"

photos/2018-06_Moucheraclette/metadata.yml

+---
+name: "9. Moucheraclette"
+cover: "DSC04034.JPG"

requirements.txt

 Jinja2
 Pillow
+pyyaml