Module diff 

Diff machinery — compare trees, index entries, and working tree files.

Overview

This module provides the core diffing infrastructure shared by diff, diff-index, status, log, show, commit, and merge.

Levels of comparison

1. Tree-to-tree — compare two tree objects (e.g. for log/show).
2. Tree-to-index — compare a tree (usually HEAD) against the index (staged changes, used by diff --cached and status).
3. Index-to-worktree — compare index against the working directory (unstaged changes, used by diff and status).

Content diff

Line-level diffing uses the Myers algorithm via the similar crate. Output formats: unified patch, raw (:old-mode new-mode ...), stat, numstat.

Structs

DiffEntry

A single diff entry representing one changed path.

SubmodulePorcelainFlags

Submodule dirty bits aligned with Git’s DIRTY_SUBMODULE_* / porcelain v2 S??? token.

Enums

DiffStatus

The kind of change between two sides of a diff.

Constants

ZERO_OID

The zero (null) object ID used for “no object” in diff output.

Functions

anchored_unified_diff

Compute a unified diff with anchored lines.

count_changes

Count insertions and deletions between two strings.

count_changes_with_algorithm

Count insertions and deletions using the given line-diff algorithm.

count_git_lines

Line count for diffstat/--numstat, matching Git’s count_lines() in diff.c.

detect_copies

Detect copies among diff entries.

detect_renames

Detect renames by pairing Deleted and Added entries with similar content.

diff_index_to_tree

Compare the index against a tree (usually HEAD’s tree).

diff_index_to_worktree

Compare the index against the working tree.

diff_tree_to_worktree

Compare a tree against the working tree.

diff_trees

Compare two trees and return the list of changed entries.

diff_trees_show_tree_entries

Like diff_trees but with show_trees flag: when true, emit entries for tree objects themselves in addition to their recursive contents (the -t flag of diff-tree).

diffcore_count_changes

Approximate copied vs added material between two blobs (Git diffcore_count_changes).

empty_blob_oid

Return the ObjectId for the empty blob object.

format_mode

Format a numeric mode as a zero-padded octal string.

format_raw

Format a diff entry in Git’s raw diff format.

format_raw_abbrev

Format a diff entry with abbreviated OIDs.

format_rename_path

Format a rename pair using Git’s compact path format.

format_stat_line

Generate diff stat output (file name + insertions/deletions).

format_stat_line_width

hash_worktree_file

head_path_states

Paths present in HEAD’s tree with mode and blob/commit OID (for status porcelain v2).

mode_from_metadata

Derive a Git file mode from filesystem metadata.

read_submodule_head_for_checkout

Read the HEAD commit OID from a submodule checkout directory.

read_submodule_head_oid

Read the HEAD commit OID from a submodule working tree directory.

rename_similarity_score

Compute rename/copy similarity percentage (0–100) between two byte slices.

rewrite_dissimilarity_index_percent

Percentage shown in dissimilarity index N% for a rewrite (similarity_index in Git’s diff.c).

rewrite_merge_score

Git merge_score from diffcore-break.c when a pair is considered broken: how much of the source blob was removed (0–[DIFF_MAX_SCORE] scale). Used for dissimilarity index metadata.

should_break_rewrite_for_stat

Whether this modified blob pair should use Git’s “complete rewrite” diffstat path when --break-rewrites is in effect (should_break in diffcore-break.c).

stat_matches

status_apply_rename_copy_detection

Apply Git-style rename and optional copy detection for index↔worktree diffs.

submodule_embedded_git_dir

Resolve the embedded git directory for a submodule work tree (sub_dir/.git).

submodule_porcelain_flags

Inspect a checked-out submodule at rel_path (relative to super_worktree) and return flags used for git status --porcelain=v2 submodule tokens.

unified_diff

Generate a unified diff patch for two blobs.

unified_diff_with_prefix

Same as unified_diff but with configurable source/destination prefixes.

unified_diff_with_prefix_and_funcname

Same as unified_diff_with_prefix with optional custom hunk-header function-name matching.

unified_diff_with_prefix_and_funcname_and_algorithm

Same as unified_diff_with_prefix_and_funcname but allows callers to choose the line diff algorithm used for hunk generation.

worktree_differs_from_index_entry

Quick stat check: does the index entry’s cached stat data match the file? Returns true when the file at ie’s path differs from the index entry (mode or blob).

zero_oid

Return the zero ObjectId.