upload: Check pre_upload right after creating commits

[jerry-skydio]

This gets us 2 things

• dry-run now runs the pre upload command, which can be a useful way
  to run the preupload on all your topics (otherwise topics marked rebase
  aren't passed to the command)
• the pre upload command will run before pausing and prompting the user.

[jerry-skydio]

Reviews in this chain:
└#312 upload: Check pre_upload right after creating commits

[jerry-skydio]

#	head	base	diff	date	summary
0	290c50f2	21108398	diff	Oct 1 18:17 PM	1 file changed, 5 insertions(+), 4 deletions(-)
1	d000a197	21108398	diff	Oct 1 18:25 PM	1 file changed, 6 insertions(+), 6 deletions(-)