Comparing Commits - Git Diff

You can generate diffs between any two versions of your project using git diff:

$ git diff master..test

That will produce the diff between the tips of the two branches. If you'd prefer to find the diff from their common ancestor to test, you can use three dots instead of two:

$ git diff master...test

git diff is an incredibly useful tool for figuring out what has changed between any two points in your project's history, or to see what people are trying to introduce in new branches, etc.

What you will commit

You will commonly use git diff for figuring out differences between your last commit, your index, and your current working directory. A common use is to simply run

$ git diff

which will show you changes in the working directory that are not yet staged for the next commit. If you want to see what is staged for the next commit, you can run

$ git diff --cached

which will show you the difference between the index and your last commit; what you would be committing if you run "git commit" without the "-a" option. Lastly, you can run

$ git diff HEAD

which shows changes in the working directory since your last commit; what you would be committing if you run "git commit -a".

More Diff Options

If you want to see how your current working directory differs from the state of the project in another branch, you can run something like

$ git diff test

This will show you what is different between your current working directory and the snapshot on the 'test' branch. You can also limit the comparison to a specific file or subdirectory by adding a path limiter:

$ git diff HEAD -- ./lib 

That command will show the changes between your current working directory and the last commit (or, more accurately, the tip of the current branch), limiting the comparison to files in the 'lib' subdirectory.

If you don't want to see the whole patch, you can add the '--stat' option, which will limit the output to the files that have changed along with a little text graph depicting how many lines changed in each file.

$>git diff --stat
 layout/book_index_template.html                    |    8 ++-
 text/05_Installing_Git/0_Source.markdown           |   14 ++++++
 text/05_Installing_Git/1_Linux.markdown            |   17 +++++++
 text/05_Installing_Git/2_Mac_104.markdown          |   11 +++++
 text/05_Installing_Git/3_Mac_105.markdown          |    8 ++++
 text/05_Installing_Git/4_Windows.markdown          |    7 +++
 .../1_Getting_a_Git_Repo.markdown                  |    7 +++-
 .../0_ Comparing_Commits_Git_Diff.markdown         |   45 +++++++++++++++++++-
 .../0_ Hosting_Git_gitweb_repoorcz_github.markdown |    4 +-
 9 files changed, 115 insertions(+), 6 deletions(-)

Sometimes that makes it easier to see overall what has changed, to jog your memory.