The way `jj git push` without arguments chooses branches pointing to
either `@` or `@-` is unusual and difficult to explain. Now that we
have `-r`, we could instead default it to `-r '@-::@'`. However, I
think it seems likely that users will want to push all local branches
leading up to `@` from the closest remote branch. That's typically
what I want. This patch changes the default to do that.
If there are branches in the revset that don't need to be pushed
because they already match the destination, we currently just print
`Nothing changed.` It seems consistent with that to also treat it as
success if there are no branches in the specified set to start
with. This patch makes the command print a warning in that case
instead.
This commit replaces the functions `UserSettings::user_name_placeholder()`` and
`UserSettings::user_email_placeholder()` with `const` `&str`s to emphasize that
the placeholder strings must not be changed to support commits without
names or email addresses made before this change.
