# Understanding Line Changes Bat Detects in Git Integration: The Complete Guide > Explore how bat enhances Git integration by detecting four line change types: Added, Modified, RemovedAbove, and RemovedBelow. Improve your code reviews today. - Repository: [David Peter/bat](https://github.com/sharkdp/bat) - Tags: deep-dive - Published: 2026-03-06 --- **Bat detects four distinct line change types in Git integration: Added (green +), Modified (yellow ~), RemovedAbove (red ‾), and RemovedBelow (red _).** When the `git` feature is enabled in the `sharkdp/bat` repository, the tool analyzes repository diffs for each displayed file and marks individual lines with specific change categories. Understanding these line changes bat detects in Git integration helps developers quickly identify code modifications directly in the terminal output. ## The Four Types of Line Changes in Bat's Git Integration The `LineChange` enum in [`src/diff.rs`](https://github.com/sharkdp/bat/blob/main/src/diff.rs) defines the four distinct categories that bat uses to classify modifications. Each variant corresponds to a specific visual indicator in the gutter. ### Added Lines **Added** lines represent new content present in the working tree but not in the index. These appear with a green **+** symbol in the left margin. In [`src/diff.rs`](https://github.com/sharkdp/bat/blob/main/src/diff.rs) (lines 10-12), the `Added` variant is defined alongside the detection logic in `get_git_diff` that identifies when `old_lines == 0 && new_lines > 0`. ### RemovedAbove Lines **RemovedAbove** indicates a deletion occurring **above** the current line number. This special case appears when a file is empty and the first line is removed, displayed with a red **‾** (overline) symbol. The detection condition in `get_git_diff` (around lines 58-76 in [`src/diff.rs`](https://github.com/sharkdp/bat/blob/main/src/diff.rs)) checks for `new_lines == 0 && old_lines > 0 && new_start == 0` to trigger this variant. ### RemovedBelow Lines **RemovedBelow** represents the standard deletion case where content has been removed **below** the current line number. This displays with a red **_** (underscore) symbol in the gutter. The logic identifies these cases when `new_lines == 0 && old_lines > 0 && new_start != 0`, distinguishing them from `RemovedAbove` based on the line position. ### Modified Lines **Modified** lines exist in both the index and working tree but have altered content. These appear with a yellow **~** (tilde) symbol. This variant serves as the fallback case in the detection logic, triggered when both old and new lines are present in the diff hunk. ## How Bat Detects Line Changes: The Implementation The core detection logic resides in the `get_git_diff` function within [`src/diff.rs`](https://github.com/sharkdp/bat/blob/main/src/diff.rs) (lines 58-76). This function processes Git diff hunks and populates a `HashMap` where keys represent line numbers and values store the detected change type. The classification follows these specific conditions: - **Added**: `old_lines == 0 && new_lines > 0` - **RemovedAbove**: `new_lines == 0 && old_lines > 0 && new_start == 0` - **RemovedBelow**: `new_lines == 0 && old_lines > 0 && new_start != 0` - **Modified**: All other cases where both old and new lines exist ## Rendering Line Changes in the Gutter Once detected, the `LineChanges` map is passed to the `LineChangesDecoration` component, which handles the visual rendering. The mapping between enum variants and display symbols occurs in [`src/decorations.rs`](https://github.com/sharkdp/bat/blob/main/src/decorations.rs) (lines 111-116): ```rust // LineChange enum definition from src/diff.rs #[derive(Copy, Clone, Debug)] pub enum LineChange { Added, // renders as green '+' RemovedAbove, // renders as red '‾' RemovedBelow, // renders as red '_' Modified, // renders as yellow '~' } ``` The decoration system caches these styled glyphs to optimize performance when rendering large files with extensive modifications. ## Practical Usage Examples To view line changes in Git-tracked files, enable the Git integration feature: ```bash # Display file with Git change indicators bat --git src/main.rs # Or set environment variable for persistent behavior export BAT_GIT=1 bat src/main.rs ``` Example output showing all four change types: ``` 1 │ fn main() { │ 2 │ println!("Hello, world!"); │ 3 │ } │ │ ──────────────────────────────── │ 4 + │ // New line added │ ← Added (green +) 5 ~ │ // Modified content │ ← Modified (yellow ~) 6 _ │ // Line below was removed │ ← RemovedBelow (red _) ``` ## Summary - Bat detects **four line change types** in Git integration: **Added**, **RemovedAbove**, **RemovedBelow**, and **Modified**. - The `LineChange` enum is defined in [`src/diff.rs`](https://github.com/sharkdp/bat/blob/main/src/diff.rs) with detection logic in the `get_git_diff` function. - **Added** lines show green **+**, **Modified** lines show yellow **~**, and removed lines display red **‾** (above) or **_** (below). - Visual rendering is handled by `LineChangesDecoration` in [`src/decorations.rs`](https://github.com/sharkdp/bat/blob/main/src/decorations.rs) using a cached glyph system. ## Frequently Asked Questions ### How does bat distinguish between RemovedAbove and RemovedBelow? Bat distinguishes these variants based on the `new_start` parameter in the diff hunk. When `new_start == 0` (indicating the start of the file), deletions are classified as `RemovedAbove` and displayed with a red overline (**‾**). When `new_start != 0`, deletions are marked as `RemovedBelow` with a red underscore (**_**). This logic is implemented in `get_git_diff` within [`src/diff.rs`](https://github.com/sharkdp/bat/blob/main/src/diff.rs). ### Can I customize the symbols used for line changes? The symbols are hardcoded in the `LineChangesDecoration` implementation in [`src/decorations.rs`](https://github.com/sharkdp/bat/blob/main/src/decorations.rs) (lines 111-116). The glyphs (**+**, **‾**, **_**, **~**) are cached as styled strings during initialization. To customize these symbols, you would need to modify the source code and recompile bat, as there are no configuration options or environment variables exposed for changing these specific indicators. ### Does bat show line changes for all files or only tracked files? Bat only displays line change indicators for files tracked by Git (or other supported version control systems). The `get_git_diff` function attempts to retrieve diff information from the repository; if the file is untracked or not in a Git repository, the `LineChanges` map remains empty and no gutter symbols are rendered. You must also ensure the `--git` flag is enabled (or `BAT_GIT=1` is set) for this feature to activate.