tools/rewrite-git-redirects.py: use canonical gitlab URLs for Repo:

```console
$ git clone https://gitlab.com/fdroid/ci-images-base.git
Cloning into 'ci-images-base'...
remote: Enumerating objects: 89, done.
remote: Counting objects: 100% (89/89), done.
remote: Compressing objects: 100% (50/50), done.
remote: Total 89 (delta 51), reused 68 (delta 39)
Unpacking objects: 100% (89/89), done.
$ rm -rf ci-images-base/
$ git clone https://gitlab.com/fdroid/ci-images-base
Cloning into 'ci-images-base'...
warning: redirecting to https://gitlab.com/fdroid/ci-images-base.git/
remote: Enumerating objects: 89, done.
remote: Counting objects: 100% (89/89), done.
remote: Compressing objects: 100% (50/50), done.
remote: Total 89 (delta 51), reused 68 (delta 39)
Unpacking objects: 100% (89/89), done.
```

tools/rewrite-git-redirects.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+#
+#
+# GitLab gives a warning every time if the git URL is redirected.  So this
+# rewrites all GitLab URLs so they are no longer a redirect.
+
+import glob
+import os
+import re
+import sys
+import yaml
+
+os.chdir(os.path.dirname(__file__) + '/../')
+
+if len(sys.argv) > 1:
+    files = sys.argv[1:]
+else:
+    files = sorted(glob.glob('metadata/*.yml'))
+
+pattern = re.compile(r'Repo: .*')
+for f in files:
+    with open(f) as fp:
+        data = yaml.load(fp)
+    repo_url = None
+    if 'Repo' in data:
+        repo_url = data['Repo'].strip().rstrip('/')
+    if repo_url and not repo_url.endswith('.git') and repo_url.startswith('https://gitlab'):
+        new_url = repo_url + '.git'
+        print("Repo:", data['Repo'], "\n -->  " + new_url + "'")
+        with open(f) as fp:
+            raw = fp.read()
+        with open(f, 'w') as fp:
+            fp.write(pattern.sub('Repo: ' + new_url, raw))