vix-git 1.4.0

Git integration: status/diff/staging via the git CLI.
Documentation
# Git

Git integration for Vix.

Two layers:

- **Pure logic** (unit-tested, no I/O): [`parse_status`] turns
`git status --porcelain` output into [`FileStatus`] rows, and [`diff_marks`]
computes per-line editor-gutter [`LineMark`]s between the committed text and
the current buffer (via the `similar` crate).
- **Runners** (shell out to the `git` CLI): [`is_repo`], [`branch`],
[`status`], [`head_blob`], and the staging/commit helpers. Using the user's
own `git` means credential helpers, SSH agents, and hooks all behave exactly
as on the command line.

## Sub-specs

- [diff-next]diff-next/index.md
- [diff-previous]diff-previous/index.md
- [git-integration]git-integration/index.md
- [git-panel]git-panel/index.md
- [stage-hunk]stage-hunk/index.md
- [toggle-diff-gutter]toggle-diff-gutter/index.md
- [unstage-hunk]unstage-hunk/index.md
- [word-diff]word-diff/index.md