squash: add -f/-t shorthands for --from/--[in]to

[avamsi]

I use these frequently and would like to type less :)

Checklist

If applicable:

• I have updated CHANGELOG.md
• I have updated the documentation (README.md, docs/, demos/)
• I have updated the config schema (cli/src/config-schema.json)
• I have added tests to cover my changes

[arxanas]

Generally, I prefer to leave -f to mean --force, so I'm not personally a fan of using -f for normal operations. (Not sure if we currently use -f elsewhere in jj or not?)

[avamsi]

move (which is deprecated in favor of squash) supports -f/-t shorthands for --from/--to.

I see your point but I don't believe jj has any commands that support --force, so maybe it's okay? But then again, --force is common enough that it'll probably creep in somewhere or the other eventually.

[avamsi]

-s/-d are probably decent alternatives (but could be confusing if we don't change --from/--to) -- that is, if there's enough interest in adding shorthands in the first place.

[yuja]

Generally, I prefer to leave -f to mean --force, so I'm not personally a fan of using -f for normal operations.

Even if we add --force-<something>, I assume we wouldn't add the short form for it. My only concern is that -f looks like --force.

[arxanas]

I don't mean to block this PR on that issue. I'll leave it to someone else to accept/reject as appropriate.

@avamsi if you're just copying the short forms from an existing command, can you add that to the commit message?

[martinvonz]

I'm also hesitant about the -f but it sounds like most people are still okay with it. So let's merge this?