Add IMAP folder tab completion

Credit for this fix goes to Reto; I guess if we're not gonna be mutt
we should probabaly do things correctly.

commands/account/cf.go

@@ -3,6 +3,7 @@ package account
 import (
 	"errors"
 
+	"git.sr.ht/~sircmpwn/aerc/commands"
 	"git.sr.ht/~sircmpwn/aerc/widgets"
 )
 
@@ -22,7 +23,7 @@ func (_ ChangeFolder) Aliases() []string {
 }
 
 func (_ ChangeFolder) Complete(aerc *widgets.Aerc, args []string) []string {
-	return nil
+	return commands.GetFolders(aerc, args)
 }
 
 func (_ ChangeFolder) Execute(aerc *widgets.Aerc, args []string) error {

commands/commands.go

@@ -3,6 +3,7 @@ package commands
 import (
 	"errors"
 	"strings"
+	"unicode"
 
 	"github.com/google/shlex"
 
@@ -108,3 +109,25 @@ func (cmds *Commands) GetCompletions(aerc *widgets.Aerc, cmd string) []string {
 	}
 	return nil
 }
+
+const caps string = "ABCDEFGHIJKLMNOPQRSTUVXYZ"
+
+func GetFolders(aerc *widgets.Aerc, args []string) []string {
+	out := make([]string, 0)
+	lower_only := false
+	for _, rune := range args[0] {
+		lower_only = lower_only || unicode.IsLower(rune)
+	}
+
+	for _, dir := range aerc.SelectedAccount().Directories().List() {
+		test := dir
+		if lower_only {
+			test = strings.ToLower(dir)
+		}
+
+		if strings.HasPrefix(test, args[0]) {
+			out = append(out, dir)
+		}
+	}
+	return out
+}

commands/msg/move.go

@@ -7,6 +7,7 @@ import (
 	"git.sr.ht/~sircmpwn/getopt"
 	"github.com/gdamore/tcell"
 
+	"git.sr.ht/~sircmpwn/aerc/commands"
 	"git.sr.ht/~sircmpwn/aerc/widgets"
 	"git.sr.ht/~sircmpwn/aerc/worker/types"
 )
@@ -22,7 +23,7 @@ func (_ Move) Aliases() []string {
 }
 
 func (_ Move) Complete(aerc *widgets.Aerc, args []string) []string {
-	return nil
+	return commands.GetFolders(aerc, args)
 }
 
 func (_ Move) Execute(aerc *widgets.Aerc, args []string) error {

widgets/dirlist.go

@@ -43,10 +43,14 @@ func NewDirectoryList(acctConf *config.AccountConfig, uiConf *config.UIConfig,
 	return dirlist
 }
 
-func (dirlist *DirectoryList) List() []string {
+func (dirlist *DirectoryList) FilteredList() []string {
 	return dirlist.dirs
 }
 
+func (dirlist *DirectoryList) List() []string {
+	return dirlist.store.List()
+}
+
 func (dirlist *DirectoryList) UpdateList(done func(dirs []string)) {
 	var dirs []string
 	dirlist.worker.PostAction(