How to use the Git command git diff

How to use the Git command git diff

The git diff is used to show differences between commits, branches, files, and more. This guide will cover the basics in addition to showing more advanced use cases of git diff.

**Basic usage of git diff

• Viewing unstaged changes:

  • To see what changes have been made locally but haven’t yet been staged for commit, run:

    git diff

    For example, this is what running git diff would look like after we update a Dockerfile to include a new base image, in addition to updating the readme to record the change.

• In this instance, the git diff command is showing us the difference between our local files and the state of those same files in the most recent commit.

• Viewing staged changes:

  • To see what changes are staged for the next commit (i.e., after git add but before git commit) run:

    git diff --staged

  • Alternatively, you can use git diff --cached, as both -staged and -cached flags serve the same purpose.

After staging our changes from the previous step with git add we can now see them by running git diff --staged

Comparing files and commits

• Diff of a specific file:

• To view changes in a specific file run:

  git diff <file-path>

• Between two commits:

• To see the differences between two commits:

  git diff <commit-id-1> <commit-id-2>

• Between two files across commits:

  • For comparing the same file across two different commits:

    git diff <commit-id-1>:<file-path> <commit-id-2>:<file-path>

• Summary of changes:

  • To get a short summary of which files changed, and the amount of additions/deletions per file, run:

    git diff --stat

Diff between branches

• Comparing branches:

  • To compare the current branch with another branch:

    git diff <branch-name>

• Diff Between specific branches:

  • To compare two specific branches:

    git diff <branch-name-1>..<branch-name-2>

Working with git diff output

• Exporting diff to a file:

  • To save the output of a diff to a file:

    git diff > diff_output.txt

Troubleshooting and tips

• git diff shows no output:

  • If git diff doesn't show any output, it could mean either there are no changes between the compared entities, or you might be comparing the same commit or branch against itself.

• Understanding the output:

  • Lines added in the diff are prefixed with a + and shown in green.

  • Lines removed are prefixed with a - and shown in red.

• Using git diff in GUI tools:

  • Many graphical Git clients and IDEs integrate git diff functionality, providing a more user-friendly interface to review changes.

For further reading please see the official git documentation.