seperate stage/ustage all files keybindings

**Is your feature request related to a problem? Please describe.**
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unstagging all files and then staged and unstaged files are combined and no longer able to retrieve staged changes.

**Describe the solution you'd like**
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unstage all files can have different keybindings, "A" instead of "a"

**Describe alternatives you've considered**
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none...

**Additional context**
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add more keybindings as well to search for file in staged/modified files. and a keybindings to jump to next/previous modified file.

Nell’issue non sono indicati file sorgente o test. Inizia individuando i punti di ingresso dei keybinding e delle voci dell’elenco dei file staged/unstaged; il lavoro è completo quando sono disponibili binding separati per fare stage e unstage di tutti i file, oltre alla ricerca richiesta e alla navigazione al file modificato successivo/precedente quando supportata.

Scritto dal modello di indicizzazione a partire dal testo della issue.