Proposal to add a shortcut for --force-with-lease

[vi0oss <vi0oss@gmail.com>]

"--force" have currently two shortcuts: "-f" and "+", hence more ergonomic.
But I expect it's better for users to use "--force-with-lease" by 
default for overriding
remote branches (e.g. cleaning up a pull request), as it rarely fails in 
normal situations.

I propose adding some shortcut for "--force-with-lease".

Options for a shortcut:

* git push origin =HEAD:master
         "=" is like "+", but weaker ('+' being typed as shift+'=')
* git push -l origin HEAD:master
* git fpush origin HEAD:master

Unfortunately hijacking "-f" to mean "--force-with-lease" is not an 
option due to scripts.
"-F" is also bad choice because of it looks like "-f" with even less 
checks (like "git checkout -B" instead of "-b").

Additionally, message when doing "git push -l" or "git push -nl" may 
show the range of commits being "thrown away".