feat: set message for multiple revsets

Allows to set the revision message of multiple revisions by passing
them as arguments. This only supports simple revisions, such as `@`,
`@-`, `xs`, and so on. Comple revisions such as `@..@-` are not
supported.

Fixes: #5

src/lib.rs

@@ -1,4 +1,3 @@
-mod cli;
 mod commit;
 mod error;
 mod jj;