commmit - enhance docs for keybinding 'c' for local branch

- closes #3030
- mention that it supports '-'
- fix documentation and builtin help

docs/keybindings/Keybindings_en.md

@@ -141,7 +141,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
 <pre>
   <kbd>&lt;c-o&gt;</kbd>: Copy branch name to clipboard
   <kbd>i</kbd>: Show git-flow options
-  <kbd>&lt;space&gt;</kbd>: Checkout
+  <kbd>&lt;space&gt;</kbd>: Checkout, use '-' for previous
   <kbd>n</kbd>: New branch
   <kbd>o</kbd>: Create pull request
   <kbd>O</kbd>: Create pull request options

pkg/i18n/english.go

@@ -868,7 +868,7 @@ func EnglishTranslationSet() TranslationSet {
 		CantRebaseOntoSelf:                  "You cannot rebase a branch onto itself",
 		CantMergeBranchIntoItself:           "You cannot merge a branch into itself",
 		ForceCheckout:                       "Force checkout",
-		CheckoutByName:                      "Checkout by name",
+		CheckoutByName:                      "Checkout by name, use '-' for previous",
 		NewBranch:                           "New branch",
 		NoBranchesThisRepo:                  "No branches for this repo",
 		CommitWithoutMessageErr:             "You cannot commit without a commit message",