commands: add expand-folder and collapse-folder

add the expand-folder and collapse-folder commands to navigate the
directory tree view. Provide keybinds for a vi-like folder navigation
experience.

Signed-off-by: Koni Marti <koni.marti@gmail.com>

commands/account/expand-folder.go

@@ -0,0 +1,42 @@
+package account
+
+import (
+	"errors"
+	"fmt"
+
+	"git.sr.ht/~rjarry/aerc/widgets"
+)
+
+type ExpandCollapseFolder struct{}
+
+func init() {
+	register(ExpandCollapseFolder{})
+}
+
+func (ExpandCollapseFolder) Aliases() []string {
+	return []string{"expand-folder", "collapse-folder"}
+}
+
+func (ExpandCollapseFolder) Complete(aerc *widgets.Aerc, args []string) []string {
+	return nil
+}
+
+func (ExpandCollapseFolder) Execute(aerc *widgets.Aerc, args []string) error {
+	if len(args) > 1 {
+		return expandCollapseFolderUsage(args[0])
+	}
+	acct := aerc.SelectedAccount()
+	if acct == nil {
+		return errors.New("No account selected")
+	}
+	if args[0] == "expand-folder" {
+		acct.Directories().ExpandFolder()
+	} else {
+		acct.Directories().CollapseFolder()
+	}
+	return nil
+}
+
+func expandCollapseFolderUsage(cmd string) error {
+	return fmt.Errorf("Usage: %s", cmd)
+}

config/binds.conf

@@ -24,6 +24,8 @@ G = :select -1<Enter>
 
 J = :next-folder<Enter>
 K = :prev-folder<Enter>
+H = :collapse-folder<Enter>
+L = :expand-folder<Enter>
 
 v = :mark -t<Enter>
 V = :mark -v<Enter>

doc/aerc.1.scd

@@ -269,6 +269,10 @@ message list, the message in the message viewer, etc).
 	Cycles to the next (or previous) folder shown in the sidebar, repeated n
 	times (default: 1).
 
+*expand-folder*, *collapse-folder*
+	Expands or collapses the current folder when the directory tree is
+	enabled.
+
 *next-result*, *prev-result*
 	Selects the next or previous search result.