Allow specifying branch instead of --stack for commit

Remove the --stack option and accept an optional branch ID or name to 
derive the stack to commit to. This lets users run commands like `but 
commit -m "message" x4` or `but commit my-branch-name`.

Changes:
- CLI: replace `--stack`/-s with a positional/optional `branch` argument.
- commit API: rename `stack_hint` to `branch_hint` and thread it through callers.
- Selection logic: update select_stack to accept a CommandContext, match exact branch names first, then attempt to parse CLI IDs and resolve branch CLI IDs to stacks, and improve error messages to reference branches.
- Main: pass `branch` through to the commit handler.

Author: schacon

crates/but/src/args.rs

@@ -61,9 +61,8 @@ pub enum Subcommands {
         /// Commit message
         #[clap(short = 'm', long = "message")]
         message: Option<String>,
-        /// Stack ID or name to commit to (if multiple stacks exist)
-        #[clap(short = 's', long = "stack")]
-        stack: Option<String>,
+        /// Branch CLI ID or name to derive the stack to commit to
+        branch: Option<String>,
         /// Only commit assigned files, not unassigned files
         #[clap(short = 'o', long = "only")]
         only: bool,

crates/but/src/commit/mod.rs

@@ -18,7 +18,7 @@ pub(crate) fn commit(
     repo_path: &Path,
     _json: bool,
     message: Option<&str>,
-    stack_hint: Option<&str>,
+    branch_hint: Option<&str>,
     only: bool,
 ) -> anyhow::Result<()> {
     let project = Project::from_path(repo_path)?;
@@ -46,7 +46,7 @@ pub(crate) fn commit(
         stacks[0].0
     } else {
         // Multiple stacks - need to select one
-        select_stack(&stacks, stack_hint)?
+        select_stack(&mut ctx, &stacks, branch_hint)?
     };
 
     // Get changes and assignments
@@ -172,20 +172,43 @@ pub(crate) fn commit(
 }
 
 fn select_stack(
+    ctx: &mut CommandContext,
     stacks: &[(but_workspace::StackId, but_workspace::ui::StackDetails)],
-    stack_hint: Option<&str>,
+    branch_hint: Option<&str>,
 ) -> anyhow::Result<but_workspace::StackId> {
-    // If a stack hint is provided, try to find it
-    if let Some(hint) = stack_hint {
-        // Try to match by branch name in stacks
+    // If a branch hint is provided, try to find it
+    if let Some(hint) = branch_hint {
+        // First, try to find by exact branch name match
         for (stack_id, stack_details) in stacks {
             for branch in &stack_details.branch_details {
                 if branch.name.to_string() == hint {
                     return Ok(*stack_id);
                 }
             }
         }
-        anyhow::bail!("Stack '{}' not found", hint);
+        
+        // If no exact match, try to parse as CLI ID
+        match crate::id::CliId::from_str(ctx, hint) {
+            Ok(cli_ids) => {
+                // Filter for branch CLI IDs and find corresponding stack
+                for cli_id in cli_ids {
+                    if let crate::id::CliId::Branch { name } = cli_id {
+                        for (stack_id, stack_details) in stacks {
+                            for branch in &stack_details.branch_details {
+                                if branch.name.to_string() == name {
+                                    return Ok(*stack_id);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+            Err(_) => {
+                // Ignore CLI ID parsing errors and continue with other methods
+            }
+        }
+        
+        anyhow::bail!("Branch '{}' not found", hint);
     }
 
     // No hint provided, show options and prompt

crates/but/src/main.rs

@@ -130,12 +130,12 @@ async fn main() -> Result<()> {
             metrics_if_configured(app_settings, CommandName::Restore, props(start, &result)).ok();
             result
         }
-        Subcommands::Commit { message, stack, only } => {
+        Subcommands::Commit { message, branch, only } => {
             let result = commit::commit(
                 &args.current_dir,
                 args.json,
                 message.as_deref(),
-                stack.as_deref(),
+                branch.as_deref(),
                 *only,
             );
             metrics_if_configured(app_settings, CommandName::Commit, props(start, &result)).ok();