feat: add --commits cli flag and Ctrl+G dual-diff toggle between files and head

[felipecm-br]

Overview

This PR introduces a convenient dual-diff toggle shortcut and a CLI startup flag that improves the workflow when navigating between uncommitted local changes and the most recent commit on HEAD.

Key Features

1. --commits CLI flag:

   • Launches lazygitrs focused directly on the Commits panel at HEAD (selection index 0).
   • Useful for shell aliases (e.g. alias lglog='lazygitrs --commits') or editor integrations specifically aimed at inspecting commit history.

2. Dual-diff toggle (Ctrl+G):

   • Easily bounce back and forth between working tree changes and HEAD:
     • When in the Files context (or when focused on a working tree diff), pressing Ctrl+G switches immediately to Commits at HEAD.
     • When in Commits, CommitFiles, or Reflog, pressing Ctrl+G switches directly back to Files.
   • Fully customizable via keybinding.universal.toggleWorkingTreeAndHead in config.yml (defaults to "<c-g>").
   • Works consistently whether sidebar or diff pane is focused.

3. Status Bar Hints & Command Palette:

   • Context-aware status bar hints dynamically show ctrl+g head when in Files and ctrl+g files when in Commits/CommitFiles.
   • Documented in the Command Palette (?) under Universal commands and Diff view commands.

Test Coverage

• Unit tests for the --commits CLI flag parsing.
• Unit tests for GUI context switching and selection reset to HEAD.
• Unit tests for Ctrl+G key event handling both in sidebar and diff-focused modes.
• Unit tests for status bar hint rendering and keybinding formatting.

[Blankeos]

Fixed and validated in 809417f: select the actual checked-out HEAD by hash (not index zero); preserve filters with a separate HEAD history view when filters/pagination exclude HEAD; honor remapped and disabled shortcuts; resolve integration with #36; and select startup HEAD after history arrives without overriding user navigation. Added regression tests for another branch ahead of HEAD, path/author/branch filters, detached and unborn HEAD, refresh, and startup. All 284 tests pass, cargo fmt --check passes, and the binary builds.

[Blankeos]

Reviewed updated implementation and validated against current main: 284 tests pass, formatting passes, and binary builds. HEAD/filter semantics and key remapping issues are addressed.

[Blankeos]

Dual-diff toggle (Ctrl+G):

Easily bounce back and forth between working tree changes and HEAD:
When in the Files context (or when focused on a working tree diff), pressing Ctrl+G switches immediately to Commits at HEAD.
When in Commits, CommitFiles, or Reflog, pressing Ctrl+G switches directly back to Files.
Fully customizable via keybinding.universal.toggleWorkingTreeAndHead in config.yml (defaults to "").
Works consistently whether sidebar or diff pane is focused.

Hi @felipecm-br I merged this PR, but I kinda went back to this particular change... I noticed this behavior actually isn't in the original lazygit. Also, I don't see how this makes it more convenient than just pressing 2 and 4 separately. It seems to be the same behavior.

Edit: I decided to remove the ctrl-G, we already have ctrl-G for "generating commit message" afterall.