[config][generic-update] Adding apply-patch, rollback, checkpoints commands (sonic-net#1536)

#### What I did
Adding apply-patch, rollback, replace, checkpoint, delete-checkpoint, list-checkpoints functionality.

#### How I did it
This PR is implementing the first step in in README.md in the design document: sonic-net/SONiC#736  

#### How to verify it
Using unit-tests

#### Previous command output (if the output of a command-line utility has changed)

#### New command output (if the output of a command-line utility has changed)

```sh
admin@sonic:~$ sudo config apply-patch --help
Usage: config apply-patch [OPTIONS] PATCH_FILE_PATH

  Apply given patch of updates to Config. A patch is a JsonPatch which
  follows rfc6902. This command can be used do partial updates to the config
  with minimum disruption to running processes. It allows addition as well
  as deletion of configs. The patch file represents a diff of ConfigDb(ABNF)
  format or SonicYang format.

  <patch-file-path>: Path to the patch file on the file-system.

Options:
  -f, --format [CONFIGDB|SONICYANG]
                                  format of config of the patch is either
                                  ConfigDb(ABNF) or SonicYang
  -d, --dry-run                   test out the command without affecting
                                  config state
  -v, --verbose                   print additional details of what the
                                  operation is doing
  -h, -?, --help                  Show this message and exit.



admin@sonic:~$ sudo config replace --help
Usage: config replace [OPTIONS] TARGET_FILE_PATH

  Replace the whole config with the specified config. The config is replaced
  with minimum disruption e.g. if ACL config is different between current
  and target config only ACL config is updated, and other config/services
  such as DHCP will not be affected. **WARNING** The target config file
  should be the whole config, not just the part intended to be updated.

  <target-file-path>: Path to the target file on the file-system.

Options:
  -f, --format [CONFIGDB|SONICYANG]
                                  format of target config is either
                                  ConfigDb(ABNF) or SonicYang
  -d, --dry-run                   test out the command without affecting
                                  config state
  -v, --verbose                   print additional details of what the
                                  operation is doing
  -h, -?, --help                  Show this message and exit.



admin@sonic:~$ sudo config rollback --help
Usage: config rollback [OPTIONS] CHECKPOINT_NAME

  Rollback the whole config to the specified checkpoint. The config is
  rolled back with minimum disruption e.g. if ACL config is different
  between current and checkpoint config only ACL config is updated, and
  other config/services such as DHCP will not be affected.

  <checkpoint-name>: The checkpoint name, use `config list-checkpoints`
  command to see available checkpoints.

Options:
  -d, --dry-run   test out the command without affecting config state
  -v, --verbose   print additional details of what the operation is doing
  -?, -h, --help  Show this message and exit.



admin@sonic:~$ sudo config checkpoint --help
Usage: config checkpoint [OPTIONS] CHECKPOINT_NAME

  Take a checkpoint of the whole current config with the specified
  checkpoint name.

  <checkpoint-name>: The checkpoint name, use `config list-checkpoints`
  command to see available checkpoints.

Options:
  -v, --verbose   print additional details of what the operation is doing
  -h, -?, --help  Show this message and exit.



admin@sonic:~$ sudo config delete-checkpoint --help
Usage: config delete-checkpoint [OPTIONS] CHECKPOINT_NAME

  Delete a checkpoint with the specified checkpoint name.

  <checkpoint-name>: The checkpoint name, use `config list-checkpoints`
  command to see available checkpoints.

Options:
  -v, --verbose   print additional details of what the operation is doing
  -h, -?, --help  Show this message and exit.



admin@sonic:~$ sudo config list-checkpoints --help
Usage: config list-checkpoints [OPTIONS]

  List the config checkpoints available.

Options:
  -v, --verbose   print additional details of what the operation is doing
  -?, -h, --help  Show this message and exit.
```

Author: ghooo

.azure-pipelines/docker-sonic-vs/Dockerfile

@@ -4,4 +4,8 @@ ARG docker_container_name
 
 ADD ["wheels", "/wheels"]
 
-RUN pip3 install --no-deps --force-reinstall /wheels/sonic_utilities-1.2-py3-none-any.whl
+# Uninstalls only sonic-utilities and does not impact its dependencies
+RUN pip3 uninstall -y sonic-utilities
+
+# Installs sonic-utilities, adds missing dependencies, upgrades out-dated depndencies
+RUN pip3 install /wheels/sonic_utilities-1.2-py3-none-any.whl

config/main.py

@@ -3,6 +3,7 @@
 import click
 import ipaddress
 import json
+import jsonpatch
 import netaddr
 import netifaces
 import os
@@ -11,6 +12,7 @@
 import sys
 import time
 
+from generic_config_updater.generic_updater import GenericUpdater, ConfigFormat
 from socket import AF_INET, AF_INET6
 from minigraph import parse_device_desc_xml
 from portconfig import get_child_ports
@@ -826,7 +828,7 @@ def cache_arp_entries():
         if filter_err:
             click.echo("Could not filter FDB entries prior to reloading")
             success = False
-    
+
     # If we are able to successfully cache ARP table info, signal SWSS to restore from our cache
     # by creating /host/config-reload/needs-restore
     if success:
@@ -987,6 +989,129 @@ def load(filename, yes):
         log.log_info("'load' executing...")
         clicommon.run_command(command, display_cmd=True)
 
+@config.command('apply-patch')
+@click.argument('patch-file-path', type=str, required=True)
+@click.option('-f', '--format', type=click.Choice([e.name for e in ConfigFormat]),
+               default=ConfigFormat.CONFIGDB.name,
+               help='format of config of the patch is either ConfigDb(ABNF) or SonicYang')
+@click.option('-d', '--dry-run', is_flag=True, default=False, help='test out the command without affecting config state')
+@click.option('-v', '--verbose', is_flag=True, default=False, help='print additional details of what the operation is doing')
+@click.pass_context
+def apply_patch(ctx, patch_file_path, format, dry_run, verbose):
+    """Apply given patch of updates to Config. A patch is a JsonPatch which follows rfc6902.
+       This command can be used do partial updates to the config with minimum disruption to running processes.
+       It allows addition as well as deletion of configs. The patch file represents a diff of ConfigDb(ABNF)
+       format or SonicYang format.
+
+       <patch-file-path>: Path to the patch file on the file-system."""
+    try:
+        with open(patch_file_path, 'r') as fh:
+            text = fh.read()
+            patch_as_json = json.loads(text)
+            patch = jsonpatch.JsonPatch(patch_as_json)
+
+        config_format = ConfigFormat[format.upper()]
+
+        GenericUpdater().apply_patch(patch, config_format, verbose, dry_run)
+
+        click.secho("Patch applied successfully.", fg="cyan", underline=True)
+    except Exception as ex:
+        click.secho("Failed to apply patch", fg="red", underline=True, err=True)
+        ctx.fail(ex)
+
+@config.command()
+@click.argument('target-file-path', type=str, required=True)
+@click.option('-f', '--format', type=click.Choice([e.name for e in ConfigFormat]),
+               default=ConfigFormat.CONFIGDB.name,
+               help='format of target config is either ConfigDb(ABNF) or SonicYang')
+@click.option('-d', '--dry-run', is_flag=True, default=False, help='test out the command without affecting config state')
+@click.option('-v', '--verbose', is_flag=True, default=False, help='print additional details of what the operation is doing')
+@click.pass_context
+def replace(ctx, target_file_path, format, dry_run, verbose):
+    """Replace the whole config with the specified config. The config is replaced with minimum disruption e.g.
+       if ACL config is different between current and target config only ACL config is updated, and other config/services
+       such as DHCP will not be affected.
+
+       **WARNING** The target config file should be the whole config, not just the part intended to be updated.
+
+       <target-file-path>: Path to the target file on the file-system."""
+    try:
+        with open(target_file_path, 'r') as fh:
+            target_config_as_text = fh.read()
+            target_config = json.loads(target_config_as_text)
+
+        config_format = ConfigFormat[format.upper()]
+
+        GenericUpdater().replace(target_config, config_format, verbose, dry_run)
+
+        click.secho("Config replaced successfully.", fg="cyan", underline=True)
+    except Exception as ex:
+        click.secho("Failed to replace config", fg="red", underline=True, err=True)
+        ctx.fail(ex)
+
+@config.command()
+@click.argument('checkpoint-name', type=str, required=True)
+@click.option('-d', '--dry-run', is_flag=True, default=False, help='test out the command without affecting config state')
+@click.option('-v', '--verbose', is_flag=True, default=False, help='print additional details of what the operation is doing')
+@click.pass_context
+def rollback(ctx, checkpoint_name, dry_run, verbose):
+    """Rollback the whole config to the specified checkpoint. The config is rolled back with minimum disruption e.g.
+       if ACL config is different between current and checkpoint config only ACL config is updated, and other config/services
+       such as DHCP will not be affected.
+
+       <checkpoint-name>: The checkpoint name, use `config list-checkpoints` command to see available checkpoints."""
+    try:
+        GenericUpdater().rollback(checkpoint_name, verbose, dry_run)
+
+        click.secho("Config rolled back successfully.", fg="cyan", underline=True)
+    except Exception as ex:
+        click.secho("Failed to rollback config", fg="red", underline=True, err=True)
+        ctx.fail(ex)
+
+@config.command()
+@click.argument('checkpoint-name', type=str, required=True)
+@click.option('-v', '--verbose', is_flag=True, default=False, help='print additional details of what the operation is doing')
+@click.pass_context
+def checkpoint(ctx, checkpoint_name, verbose):
+    """Take a checkpoint of the whole current config with the specified checkpoint name.
+
+       <checkpoint-name>: The checkpoint name, use `config list-checkpoints` command to see available checkpoints."""
+    try:
+        GenericUpdater().checkpoint(checkpoint_name, verbose)
+
+        click.secho("Checkpoint created successfully.", fg="cyan", underline=True)
+    except Exception as ex:
+        click.secho("Failed to create a config checkpoint", fg="red", underline=True, err=True)
+        ctx.fail(ex)
+
+@config.command('delete-checkpoint')
+@click.argument('checkpoint-name', type=str, required=True)
+@click.option('-v', '--verbose', is_flag=True, default=False, help='print additional details of what the operation is doing')
+@click.pass_context
+def delete_checkpoint(ctx, checkpoint_name, verbose):
+    """Delete a checkpoint with the specified checkpoint name.
+
+       <checkpoint-name>: The checkpoint name, use `config list-checkpoints` command to see available checkpoints."""
+    try:
+        GenericUpdater().delete_checkpoint(checkpoint_name, verbose)
+
+        click.secho("Checkpoint deleted successfully.", fg="cyan", underline=True)
+    except Exception as ex:
+        click.secho("Failed to delete config checkpoint", fg="red", underline=True, err=True)
+        ctx.fail(ex)
+
+@config.command('list-checkpoints')
+@click.option('-v', '--verbose', is_flag=True, default=False, help='print additional details of what the operation is doing')
+@click.pass_context
+def list_checkpoints(ctx, verbose):
+    """List the config checkpoints available."""
+    try:
+        checkpoints_list = GenericUpdater().list_checkpoints(verbose)
+        formatted_output = json.dumps(checkpoints_list, indent=4)
+        click.echo(formatted_output)
+    except Exception as ex:
+        click.secho("Failed to list config checkpoints", fg="red", underline=True, err=True)
+        ctx.fail(ex)
 
 @config.command()
 @click.option('-y', '--yes', is_flag=True)
@@ -2581,8 +2706,8 @@ def add(ctx, interface_name, ip_addr, gw):
         if interface_name is None:
             ctx.fail("'interface_name' is None!")
 
-    # Add a validation to check this interface is not a member in vlan before 
-    # changing it to a router port 
+    # Add a validation to check this interface is not a member in vlan before
+    # changing it to a router port
     vlan_member_table = config_db.get_table('VLAN_MEMBER')
     if (interface_is_in_vlan(vlan_member_table, interface_name)):
             click.echo("Interface {} is a member of vlan\nAborting!".format(interface_name))