when "shore bump" updates package.yaml files, it triggers an update

src/shore/__main__.py

@@ -299,7 +299,8 @@ def checks(treat_warnings_as_errors):
 @cli.command('update')
 @click.option('--skip-checks', is_flag=True)
 @click.option('--dry', is_flag=True)
-def update(skip_checks, dry):
+@click.option('--stage', is_flag=True, help='Stage changed files in Git.')
+def update(skip_checks, dry, stage):
   """ (Re-)render files managed shore. """
 
   def _collect_files(subject):
@@ -318,6 +319,9 @@ def update(skip_checks, dry):
     if not dry:
       write_to_disk(file)
 
+  if stage:
+    _git.add([f.name for f in files])
+
 
 @cli.command('verify')
 @click.option('--tag', '-t', help='Specify the tag from CI checks to match with the tag produced by shore.')
@@ -497,6 +501,15 @@ def bump(**args):
         with open(group_key, 'w') as fp:
           fp.write(content)
 
+    if args['tag'] and version_sel_refs:
+      logger.warning('bump requires an update in order to automatically tag')
+      _cache.clear()
+      try:
+        update(['--stage'])
+      except SystemExit as exc:
+        if exc.code != 0:
+          raise
+
   if args['tag']:
     if any(f.mode == 'A' for f in _git.porcelain()):
       logger.error('cannot tag with non-empty staging area')

src/shore/util/git.py

@@ -27,6 +27,11 @@ Branch = collections.namedtuple('Branch', 'name,current')
 FileStatus = collections.namedtuple('FileStatus', 'mode,filename')
 
 
+def add(files: List[str], path: str = None):
+  command = ['git', 'add', '--'] + files
+  subprocess.check_call(command, cwd=path)
+
+
 def branches(path: str = None) -> List[Branch]:
   command = ['git', 'branch']
   results = []