Config for deleting message from message viewer

As suggested in #268, this adds a behaviour setting for
deleting message from message viewer.

commands/msg/delete.go

@@ -47,7 +47,7 @@ func (Delete) Execute(aerc *widgets.Aerc, args []string) error {
 	store.Next()
 	if isMsgView {
 		nextMsg := store.Selected()
-		if nextMsg == msg {
+		if nextMsg == msg || !aerc.Config().Ui.NextMessageOnDelete {
 			aerc.RemoveTab(widget)
 			acct.Messages().Scroll()
 		} else {

config/aerc.conf.in

@@ -57,6 +57,11 @@ dirlist-format=%n %>r
 # Default: ""
 sort=
 
+# Moves to next message when the current message is deleted
+#
+# Default: false
+next-message-on-delete=true
+
 [viewer]
 #
 # Specifies the pager to use when displaying emails. Note that some filters

config/config.go

@@ -37,6 +37,7 @@ type UIConfig struct {
 	SpinnerDelimiter    string   `ini:"spinner-delimiter"`
 	DirListFormat       string   `ini:"dirlist-format"`
 	Sort                []string `delim:" "`
+	NextMessageOnDelete bool     `ini:"next-message-on-delete"`
 }
 
 const (
@@ -356,6 +357,7 @@ func LoadConfigFromFile(root *string, sharedir string) (*AercConfig, error) {
 			Spinner:             "[..]    , [..]   ,  [..]  ,   [..] ,    [..],   [..] ,  [..]  , [..]   ",
 			SpinnerDelimiter:    ",",
 			DirListFormat:       "%n %>r",
+			NextMessageOnDelete: true,
 		},
 
 		Viewer: ViewerConfig{

doc/aerc-config.5.scd

@@ -150,6 +150,11 @@ These options are configured in the *[ui]* section of aerc.conf.
 |  %>X
 :  make format specifier 'X' be right justified
 
+*next-message-on-delete*
+	Moves to next message when the current message is deleted
+
+	Default: true
+
 ## VIEWER
 
 These options are configured in the *[viewer]* section of aerc.conf.