docs: add FAQ for why to use new-then-amend over edit

cli/src/commands/edit.rs

@@ -25,6 +25,8 @@ use crate::ui::Ui;
 ///
 /// Note, it is generally recommended to instead to use `jj new` and `jj amend`. Creating
 /// a new revision enables being more intentional with respect to the existing revision.
+///
+/// For more information, see https://github.com/martinvonz/jj/blob/main/docs/FAQ.md#how-do-i-resume-working-on-an-existing-change
 #[derive(clap::Args, Clone, Debug)]
 pub(crate) struct EditArgs {
     /// The commit to edit

docs/FAQ.md

@@ -137,6 +137,17 @@ 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.
 
+### How do I resume working on an existing change?
+
+There are two ways to resume working on an earlier change: `jj new` then `jj amend`,
+and `jj edit`. The first is generally recommended over the second for a few reasons,
+which come down to how intentional you are with your changes. If the revision you 
+want to resume working on has a conflict, `jj edit` would restore the state with
+plain-text conflict annotations. Editing those annotations incorrectly or by
+accident can lead to undesired output from conflict resolution. If you amend a new
+revision onto a revision that contains a conflict, the conflict will be updated to
+correctly reflect your new changes.
+
 ### How do I deal with divergent changes ('??' after the [change ID])?
 
 A [divergent change][glossary_divergent_change] represents a change that has two