git-diff-index

Compare the working directory with a specific commit

$ git diff-index [commit]

$ git diff-index [commit] [path/to/file_or_directory]

$ git diff-index --cached [commit]

$ git diff-index --quiet [commit]

git diff-index [options] [<tree-ish>] [--] [<path…>]

-m
    Detect renames and copies more aggressively during merge diffs

-p, --patch
    Generate plain patches showing hunk headers and context

-u
    Synonym for -p, generate unified diffs (deprecated)

--no-index
    Compare two directories without Git repository (rare for diff-index)

--cached
    Compare index/tree-ish to index itself (limited use)

--patch-with-stat
    Combined --stat and -p output

--no-color
    Suppress colored diff output

--color[=<when>]
    Enable color (always, never, auto)

--word-diff[=<mode>]
    Show word-level diffs (plain, color, porcelain)

--stat
    Generate diffstat summary (lines changed per file)

--summary
    One-line summary per file (added/removed/renamed)

-R
    Swap input/output for reverse diff

--full-index
    Show full object names, not abbreviated

--binary
    Diff binary files as base64 (well or raw)

--abbrev[=<n>]
    Use n-digit object name abbreviations

--ext-diff
    Use external diff driver

--no-ext-diff
    Disable external diff driver

--textconv
    Use textconv filters

--no-textconv
    Disable textconv filters

--ignore-submodules[=<when>]
    Ignore submodule changes (none, untracked, dirty, all)

--src-prefix=<prefix>
    Set source prefix for "a/" in paths

--dst-prefix=<prefix>
    Set destination prefix for "b/" in paths

--no-prefix
    Omit a/ and b/ path prefixes

-q, --quiet
    No output, exit 1 on differences

--relative[=<path>]
    Make paths relative to given directory

--submodule[=<format>]
    Diff submodule commits (diff, short)

--relative-submodules
    Use relative paths for submodules

git diff-index is a low-level Git porcelain command that compares the content and file modes (permissions) of blobs in the index (staging area) or a specified <tree-ish> against the corresponding files in the working tree.

Without a <tree-ish>, it diffs the current index against the working directory, revealing unstaged changes or discrepancies between staged content and disk files. When provided a <tree-ish> (like HEAD), it compares that tree's blobs to the working tree, useful for viewing changes since a specific commit.

Output defaults to a list of differing paths with status (e.g., modified, deleted). Options enable summaries, patches, stats, or quiet mode. It ignores untracked files and focuses only on tracked paths matching the <pathspec>.

Ideal for scripts checking if the working tree matches the index before commits, or generating diffs in automation. Supports advanced formatting like word diffs, color, and submodule handling, inheriting options from the git diff family.

Ignores untracked files; does not detect new files unless in index. Output format sensitive to diff.algorithm config. Not for interactive use—prefer git diff.

0 if identical or no changes; 1 if differences found; >1 on errors.
git diff-index --quiet HEAD checks if working tree clean vs HEAD.

git diff-index HEAD: Working tree vs last commit.
git diff-index: Index vs working tree.
Use --name-only (inherited) for paths only.

Introduced in Git v0.99 (2005) as core plumbing command by Linus Torvalds. Evolved with diff family options; stabilized in Git 1.5+ (2007). Remains essential for scripts despite high-level alternatives like git diff.

git-diff-files(1), git-diff-tree(1), git-diff(1), git-status(1)