adds more intelligent save logic and diff to network config modules (#26565)

* adds more intelligent save logic and diff to network config modules

* adds sha1 property to NetworkConfig
* adds new argument save_when to argument_spec
* adds new argument diff_against to argument_spec
* adds new argument intended_config to argument_spec
* renames config argument to running_config with alias to config
* deprecates the use of the save argument
* before and after now work with src argument
* misc module clean

Modules updated
* nxos_config
* ios_config
* eos_config

Most notably this makes the save mechanism more intelligent for config
modules for devices that need to copy the ephemeral config to
non-volatile storage.

The diff_against argument allows the playbook task to control what the
device's running-config is diff'ed against. By default it will return
the diff of the startup-config.

* removes ios_config from pep8/legacy_files.txt

* extends the ignore lines argument to the module

* clean up CI errors

* add missing list brackets

* fixes typo

* fixes unit test cases

* remove last line break when returning config contents

* encode config string to bytes before hashing

* fix typo

* addresses feedback in PR

* update unit test cases

lib/ansible/module_utils/netcfg.py

@@ -26,12 +26,20 @@
 # USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 import re
+import hashlib
 
 from ansible.module_utils.six.moves import zip
+from ansible.module_utils._text import to_bytes
 from ansible.module_utils.network_common import to_list
 
 DEFAULT_COMMENT_TOKENS = ['#', '!', '/*', '*/', 'echo']
 
+DEFAULT_IGNORE_LINES_RE = set([
+    re.compile("Using \d+ out of \d+ bytes"),
+    re.compile("Building configuration"),
+    re.compile("Current configuration : \d+ bytes")
+])
+
 
 class ConfigLine(object):
 
@@ -97,6 +105,9 @@ def ignore_line(text, tokens=None):
     for item in (tokens or DEFAULT_COMMENT_TOKENS):
         if text.startswith(item):
             return True
+    for regex in DEFAULT_IGNORE_LINES_RE:
+        if regex.match(text):
+            return True
 
 
 def _obj_to_text(x):
@@ -141,9 +152,16 @@ def dumps(objects, output='block', comments=False):
 
 class NetworkConfig(object):
 
-    def __init__(self, indent=1, contents=None):
+    def __init__(self, indent=1, contents=None, ignore_lines=None):
         self._indent = indent
         self._items = list()
+        self._config_text = None
+
+        if ignore_lines:
+            for item in ignore_lines:
+                if not isinstance(item, re._pattern_type):
+                    item = re.compile(item)
+                DEFAULT_IGNORE_LINES_RE.add(item)
 
         if contents:
             self.load(contents)
@@ -152,6 +170,16 @@ class NetworkConfig(object):
     def items(self):
         return self._items
 
+    @property
+    def config_text(self):
+        return self._config_text
+
+    @property
+    def sha1(self):
+        sha1 = hashlib.sha1()
+        sha1.update(to_bytes(str(self), errors='surrogate_or_strict'))
+        return sha1.digest()
+
     def __getitem__(self, key):
         for line in self:
             if line.text == key:
@@ -168,6 +196,7 @@ class NetworkConfig(object):
         return len(self._items)
 
     def load(self, s):
+        self._config_text = s
         self._items = self.parse(s)
 
     def loadfp(self, fp):