split out cli validation from executionv1.13.5

A common pattern in our subcommands is to verify the arguments &
options before executing things.  For some subcommands, that check
stage is quite long which makes the execution function even bigger.
Lets split that logic out of the execute phase so it's easier to
manage these.

This is most noticeable in the sync subcommand whose Execute func
is quite large, and the option checking makes up ~15% of it.

The manifest command's Execute can be simplified significantly as
the optparse configuration always sets output_file to a string.

Change-Id: I7097847ff040e831345e63de6b467ee17609990e
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/234834
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Mike Frysinger <vapier@google.com>

1 files changed, 3 insertions, 8 deletions

diff --git a/subcmds/manifest.py b/subcmds/manifest.py
index 07fa323a..768f072e 100644
--- a/subcmds/manifest.py
+++ b/subcmds/manifest.py
@@ -73,14 +73,9 @@ in a Git repository for use during future 'repo init' invocations.
     if opt.output_file != '-':
       print('Saved manifest to %s' % opt.output_file, file=sys.stderr)
 
-  def Execute(self, opt, args):
+  def ValidateOptions(self, opt, args):
     if args:
       self.Usage()
 
-    if opt.output_file is not None:
-      self._Output(opt)
-      return
-
-    print('error: no operation to perform', file=sys.stderr)
-    print('error: see repo help manifest', file=sys.stderr)
-    sys.exit(1)
+  def Execute(self, opt, args):
+    self._Output(opt)