Difference between a git commit and the working directory?
The git-diff manual pages says that git diff is used to
Show changes between the working tree and the index or a tree, changes between the index and a tree, changes between two trees, or changes between two files on disk.
But what about if you want to show the difference between a commit prior to HEAD and the working directory? Is that possible?
Answer
Yes, but it depends a bit on your definition on what the “current project state” is. The manual for git diff goes on.
If you are interested in comparing with the staged changes:
git diff [--options] --cached [<commit>] [--] [<path>...]This form is to view the changes you staged for the next commit relative to the named
<commit>. Typically you would want comparison with the latest commit, so if you do not give<commit>, it defaults to HEAD. If HEAD does not exist (e.g. unborned branches) and<commit>is not given, it shows all staged changes.--stagedis a synonym of--cached.
If you are interested in comparing with the unstaged changes:
git diff [--options] <commit> [--] [<path>...]This form is to view the changes you have in your working tree relative to the named
<commit>. You can use HEAD to compare it with the latest commit, or a branch name to compare with the tip of a different branch.
Or if you are just interested in comparing any two commits (one could be HEAD):
git diff [--options] <commit> <commit> [--] [<path>...]This is to view the changes between two arbitrary
<commit>s.
So you might want to run git diff someOldCommit HEAD to see the differences between someOldCommit and the current HEAD.