support reverse tabbing (#92)

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+- support reverse tabbing using shift+tab ([#92](https://github.com/extrawurst/gitui/issues/92))
+
 ## [0.4.0] - 2020-05-25
 
 ### Added

src/app.rs

@@ -128,7 +128,11 @@ impl App {
         } else if let Event::Key(k) = ev {
             let new_flags = match k {
                 keys::TAB_TOGGLE => {
-                    self.toggle_tabs()?;
+                    self.toggle_tabs(false)?;
+                    NeedsUpdate::COMMANDS
+                }
+                keys::TAB_TOGGLE_REVERSE => {
+                    self.toggle_tabs(true)?;
                     NeedsUpdate::COMMANDS
                 }
 
@@ -235,12 +239,14 @@ impl App {
         ]
     }
 
-    fn toggle_tabs(&mut self) -> Result<()> {
-        let mut new_tab = self.tab + 1;
-        {
-            let tabs = self.get_tabs();
-            new_tab %= tabs.len();
-        }
+    fn toggle_tabs(&mut self, reverse: bool) -> Result<()> {
+        let tabs_len = self.get_tabs().len();
+        let new_tab = if reverse {
+            self.tab.wrapping_sub(1).min(tabs_len.saturating_sub(1))
+        } else {
+            self.tab.saturating_add(1) % tabs_len
+        };
+
         self.set_tab(new_tab)
     }
 

src/keys.rs

@@ -15,6 +15,7 @@ const fn with_mod(
 }
 
 pub const TAB_TOGGLE: KeyEvent = no_mod(KeyCode::Tab);
+pub const TAB_TOGGLE_REVERSE: KeyEvent = no_mod(KeyCode::BackTab);
 pub const FOCUS_WORKDIR: KeyEvent = no_mod(KeyCode::Char('1'));
 pub const FOCUS_STAGE: KeyEvent = no_mod(KeyCode::Char('2'));
 pub const FOCUS_RIGHT: KeyEvent = no_mod(KeyCode::Right);