Add keep_by_hours option

To be more adaptive to user needs, keep_by_hours option works as the
inverse of the "delete_by_hours" option. "keep_by_hours" will keep
any tag newer than the specified number of hours.

registry.py

@@ -58,7 +58,7 @@ class Requests:
             print('[debug][registry][request]: {0} {1}'.format(method, url))
             if 'Authorization' in kwargs['headers']:
                 print('[debug][registry][request]: Authorization header:')
-                
+
                 token_parsed = kwargs['headers']['Authorization'].split('.')
                 pprint.pprint(ast.literal_eval(decode_base64(token_parsed[0])))
                 pprint.pprint(ast.literal_eval(decode_base64(token_parsed[1])))
@@ -67,12 +67,12 @@ class Requests:
         if str(res.status_code)[0] == '2':
             if DEBUG: print("[debug][registry] accepted")
             return (res, kwargs['headers']['Authorization'])
-        
+
         if res.status_code == 401:
             if DEBUG: print("[debug][registry] Access denied. Refreshing token...")
             oauth = www_authenticate.parse(res.headers['Www-Authenticate'])
 
-            if DEBUG: 
+            if DEBUG:
                 print('[debug][auth][answer] Auth header:')
                 pprint.pprint(oauth['bearer'])
 
@@ -81,11 +81,11 @@ class Requests:
                 oauth['bearer']['service'],
                 oauth['bearer']['scope'])
 
-            if DEBUG: 
+            if DEBUG:
                 print('[debug][auth][request] Refreshing auth token: POST {0}'.format(request_url))
-                
+
             try_oauth = requests.post(request_url, auth=auth, **kwargs)
-           
+
             try:
                 token = ast.literal_eval(try_oauth._content)['token']
             except SyntaxError:
@@ -101,7 +101,7 @@ class Requests:
             kwargs['headers']['Authorization'] = 'Bearer {0}'.format(token)
         else:
             return (res, kwargs['headers']['Authorization'])
-        
+
         res = requests.request(method, url, **kwargs)
         return (res, kwargs['headers']['Authorization'])
 
@@ -151,11 +151,11 @@ def get_auth_schemes(r,path):
          - www-authenticate: basic
          - www-authenticate: bearer
     """
-    
+
     if DEBUG: print("[debug][funcname]: get_auth_schemes()")
 
     try_oauth = requests.head('{0}{1}'.format(r.hostname,path), verify=not r.no_validate_ssl)
-        
+
     if 'Www-Authenticate' in try_oauth.headers:
         oauth = www_authenticate.parse(try_oauth.headers['Www-Authenticate'])
         if DEBUG:
@@ -501,7 +501,14 @@ for more detail on garbage collection read here:
 
     parser.add_argument(
         '--delete-by-hours',
-        help=('Will delete all tags that older than specified hours. Be careful!'),
+        help=('Will delete all tags that are older than specified hours. Be careful!'),
+        default=False,
+        nargs='?',
+        metavar='Hours')
+
+    parser.add_argument(
+        '--keep-by-hours',
+        help=('Will keep all tags that are newer than specified hours.'),
         default=False,
         nargs='?',
         metavar='Hours')
@@ -605,11 +612,35 @@ def delete_tags_by_age(registry, image_name, dry_run, hours, tags_to_keep):
     delete_tags(registry, image_name, dry_run, tags_to_delete, tags_to_keep)
 
 
+def get_newer_tags(registry, image_name, hours, tags_list):
+    newer_tags = []
+    print('---------------------------------')
+    for tag in tags_list:
+        image_config = registry.get_tag_config(image_name, tag)
+
+        if image_config == []:
+            print("tag not found")
+            continue
+
+        image_age = registry.get_image_age(image_name, image_config)
+
+        if image_age == []:
+            print("timestamp not found")
+            continue
+
+        if dt.strptime(image_age[:-4], "%Y-%m-%dT%H:%M:%S.%f") >= dt.now() - timedelta(hours=int(hours)):
+            print("Keeping tag: {0} timestamp: {1}".format(
+                tag, image_age))
+            newer_tags.append(tag)
+
+    return newer_tags
+
+
 def main_loop(args):
     global DEBUG
 
     DEBUG = True if args.debug else False
-    
+
     keep_last_versions = int(args.num)
 
     if args.no_validate_ssl:
@@ -644,9 +675,9 @@ def main_loop(args):
 
     registry = Registry.create(args.host, args.login, args.no_validate_ssl,
                                args.digest_method)
-    
+
     registry.auth_schemes = get_auth_schemes(registry,'/v2/_catalog')
-    
+
     if args.delete:
         print("Will delete all but {0} last tags".format(keep_last_versions))
 
@@ -682,10 +713,14 @@ def main_loop(args):
                             layer['blobSum']))
 
         # add tags to "tags_to_keep" list, if we have regexp "tags_to_keep"
-        # entries:
+        # entries or a number of hours for "keep_by_hours":
         keep_tags = []
         if args.keep_tags_like:
             keep_tags.extend(get_tags_like(args.keep_tags_like, tags_list))
+        if args.keep_by_hours:
+            keep_tags.extend(get_newer_tags(registry, image_name,
+                                            args.keep_by_hours, tags_list))
+        keep_tags = list(set(keep_tags))  # Eliminate duplicates
 
         # delete tags if told so
         if args.delete or args.delete_all: