cli branch create/set: add --at/--to aliases to -r

Now that `jj move` does not accept `-r`, `jj set --to` seems more useful
than `jj set -r`.

I am not sure whether `-r` should be kept or removed.

I was also considering adding `create --to` as alias for `create -r`,
but I am hoping `--at` will be easy enough to remember since it's the
preposition one would think of.

cli/src/commands/branch/create.rs

@@ -25,7 +25,7 @@ use crate::ui::Ui;
 #[derive(clap::Args, Clone, Debug)]
 pub struct BranchCreateArgs {
     /// The branch's target revision
-    #[arg(long, short)]
+    #[arg(long, short, visible_alias = "at")]
     revision: Option<RevisionArg>,
 
     /// The branches to create

cli/src/commands/branch/set.rs

@@ -25,7 +25,7 @@ use crate::ui::Ui;
 #[derive(clap::Args, Clone, Debug)]
 pub struct BranchSetArgs {
     /// The branch's target revision
-    #[arg(long, short)]
+    #[arg(long, short, visible_alias = "to")]
     revision: Option<RevisionArg>,
 
     /// Allow moving the branch backwards or sideways

docs/FAQ.md

@@ -134,10 +134,8 @@ Use `jj obslog -p` to see how your working-copy commit has evolved. Find the
 commit you want to restore the contents to. Let's say the current commit (with
 the changes intended for a new commit) are in commit X and the state you wanted
 is in commit Y. Note the commit id (normally in blue at the end of the line in
-the log output) of each of them. Now use `jj new` to create a new working-copy
-commit, then run `jj restore --from Y --to @-` to restore the parent commit
-to the old state, and `jj restore --from X` to restore the new working-copy
-commit to the new state.
+the log output) of each of them. Now use `jj split --restore-from Y` to split
+the current commit into its old version and the changes since then.
 
 ### How do I resume working on an existing change?