git-diff-index - Linux

Overview

git-diff-index compares the contents of a staged file in the index to either the working copy (if specified) or the version from a given tree or commit (if not). It’s useful for reviewing changes, checking for errors before committing, and verifying the results of merging, cherry-picking, and other operations.

Syntax

git diff-index [-a|-b|-c|-r] [--cached] [--diff-filter=<filter>]
              [--ignore-errors] [--ignore-file=<file>]
              [--ignore-submodules] [--ignore-untracked] [--no-binary]
              [--no-color] [--no-extensions] [--no-index] [--no-renames]
              [--no-verify] [--numstat] [--pathname=<path>] [--pickaxe-regex=<regex>]
              [--quiet] [--staged] [--trust-mtime] [--<option>] [--no-<option>]
              [--] <tree-ish> <path>...

Options/Flags

-a, –all: Diff all staged files.
-b, –brief: Show fewer details in the output.
-c, –cached: Use the staged file contents.
-r, –relative: Display paths relative to the current directory.
–cached: Compare between staged and HEAD.
–diff-filter: Specifies the changes to display (e.g., ‘A’, ‘D’, ‘M’).
–ignore-errors: Ignore errors when reading the index.
–ignore-file: Exclude specific patterns from the diff.
–ignore-submodules: Don’t descend into submodules.
–ignore-untracked: Ignore untracked files.
–no-binary: Display files in text format, even if they’re binary.
–no-color: Disable color output.
–no-extensions: Ignore version control extensions.
–no-index: Don’t use the index.
–no-renames: Don’t show renamed files.
–no-verify: Don’t verify the signature of the file in the index.
–numstat: Display summary of file changes as number of added/deleted lines.
–pathname: Specify a custom diff output format.
–pickaxe-regex: Use the given regex to match hunk headers.
–quiet: Suppress output except error messages.
–staged: Compare between staged and unstaged changes.
–trust-mtime: Trust the mtime of the file.

Examples

Compare staged changes to the working copy:
```
git diff-index --cached
```
Compare a specific file to the index:
```
git diff-index --cached -- myfile.txt
```
Diff all staged files, filtering out renamed ones:
```
git diff-index HEAD -- . --no-renames
```
Display a summary of changes:
```
git diff-index --cached --numstat
```

Compare index to a specific commit:

git diff-index 12345 HEAD -- myfile.txt

Common Issues

No arguments provided: Specify either a tree-ish and paths or the --cached flag to specify a comparison against the HEAD.
File not found in index: The file is not staged. Use git add to add it to the index.
Corrupted index: Reset the index using git reset or re-initialize it with git init.

Integration

git-diff-index can be combined with other Git commands to perform advanced tasks:

Compare staged changes to a remote branch:

git fetch origin
git diff-index origin/main HEAD

Check for uncommitted changes in a subdirectory:

git diff-index --cached --no-ignore-submodules subdirectory

Related Commands

git diff: Compares changes between two trees or commits.
git status: Shows the changes in the working directory and the index.
git checkout: Overwrites local files with either the index or a tree/commit.
git add: Adds files to the index.