docs: Add ASCII graphs to interdiff, squash, and duplicate help

This addresses #3687 by adding visual ASCII diagrams to the help text
of commands that work with commit graphs:

- interdiff: Shows how commits are compared by rebasing
- squash: Shows how changes are moved between commits
- duplicate: Shows how commits are copied onto their parents or new destinations

Added #[command(verbatim_doc_comment)] to preserve the ASCII art formatting.

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

Author: murataslan1

cli/src/commands/duplicate.rs

@@ -41,16 +41,35 @@ use crate::ui::Ui;
 /// are provided, commits will be duplicated onto their existing parents or onto
 /// other newly duplicated commits.
 ///
+/// ```text
+/// C        C  C'
+/// |   =>   | /
+/// B        B
+/// ```
+/// (C is duplicated to C', both have the same parent B)
+///
 /// When any of the `--onto`, `--insert-after`, or `--insert-before` arguments
 /// are provided, the roots of the specified commits will be duplicated onto the
 /// destination indicated by the arguments. Other specified commits will be
 /// duplicated onto these newly duplicated commits. If the `--insert-after` or
 /// `--insert-before` arguments are provided, the new children indicated by the
 /// arguments will be rebased onto the heads of the specified commits.
 ///
+/// ```text
+/// C          C'
+/// |          |
+/// B    =>    D
+/// |          |
+/// A   D      B   C
+///      \      \ /
+///       E      A   E
+/// ```
+/// (duplicating C onto D with `jj duplicate C --onto D`)
+///
 /// By default, the duplicated commits retain the descriptions of the originals.
 /// This can be customized with the `templates.duplicate_description` setting.
 #[derive(clap::Args, Clone, Debug)]
+#[command(verbatim_doc_comment)]
 pub(crate) struct DuplicateArgs {
     /// The revision(s) to duplicate (default: @)
     #[arg(

cli/src/commands/interdiff.rs

@@ -32,7 +32,25 @@ use crate::ui::Ui;
 /// This excludes changes from other commits by temporarily rebasing `--from`
 /// onto `--to`'s parents. If you wish to compare the same change across
 /// versions, consider `jj evolog -p` instead.
+///
+/// For example, with `jj interdiff --from A --to C`:
+///
+/// ```text
+///     D
+///     |
+/// C   C
+/// |   |
+/// B   A'  (A rebased onto C's parent)
+/// |   |
+/// A   B
+///  \ /
+///   root
+/// ```
+///
+/// The command compares A' (A rebased onto B) with C, effectively showing
+/// what changed between the two commits independent of their different bases.
 #[derive(clap::Args, Clone, Debug)]
+#[command(verbatim_doc_comment)]
 #[command(group(ArgGroup::new("to_diff").args(&["from", "to"]).multiple(true).required(true)))]
 #[command(mut_arg("ignore_all_space", |a| a.short('w')))]
 #[command(mut_arg("ignore_space_change", |a| a.short('b')))]

cli/src/commands/squash.rs

@@ -55,6 +55,16 @@ use crate::ui::Ui;
 /// parent revision. Fails if there are several parent revisions (i.e., the
 /// given revision is a merge).
 ///
+/// ```text
+/// D          D
+/// |          |
+/// C    =>   B'  (contains changes from both B and C; C is abandoned)
+/// |          |
+/// B          A
+/// |
+/// A
+/// ```
+///
 /// With the `--from` and/or `--into` options, moves changes from/to the given
 /// revisions. If either is left out, it defaults to the working-copy commit.
 /// For example, `jj squash --into @--` moves changes from the working-copy
@@ -78,6 +88,7 @@ use crate::ui::Ui;
 /// together with one or more `--from` options (if no `--from` is specified,
 /// `--from @` is assumed).
 #[derive(clap::Args, Clone, Debug)]
+#[command(verbatim_doc_comment)]
 pub(crate) struct SquashArgs {
     /// Revision to squash into its parent (default: @). Incompatible with the
     /// experimental `-o`/`-A`/`-B` options.