What's the equivalent of git diff?

[vincentfiestada]

How can I compare the working tree to a Commit or Tree object? This would be the equivalent of running git diff in the console.

[pjbgf]

Here's an extract from a test in plumbing/object which compares two trees:

func (s *TreeSuite) TestTreeDiff(c *C) {
	f := fixtures.ByURL("https://github.com/src-d/go-git.git").One()
	storer := filesystem.NewStorage(f.DotGit(), cache.NewObjectLRUDefault())
	commit, err := GetCommit(storer, plumbing.NewHash("89f8bda31d29767a6d6ba8f9d0dfb941d598e843"))
	c.Assert(err, IsNil)

	tree, err := commit.Tree()
	c.Assert(err, IsNil)

	parentCommit, err := commit.Parent(0)
	c.Assert(err, IsNil)

	parentTree, err := parentCommit.Tree()
	c.Assert(err, IsNil)

	ch, err := parentTree.Diff(tree)
	c.Assert(err, IsNil)

	c.Assert(ch, HasLen, 3)
	c.Assert(ch[0].From.Name, Equals, "examples/object_storage/main.go")
	c.Assert(ch[0].To.Name, Equals, "examples/storage/main.go")

	ch, err = parentTree.DiffContext(context.Background(), tree)
	c.Assert(err, IsNil)
	c.Assert(ch, HasLen, 3)
}

https://github.com/go-git/go-git/blob/master/plumbing/object/tree_test.go#L244-L269

With the resulting ch you probably could use the upstream DiffPrettyText to transform that into text:

[aslakhellesoy]

@vincentfiestada did you find out how to do this?

I don't see how @pjbgf's example above builds a Tree from a Worktree - the code is doing it from a commit (89f8bda31d29767a6d6ba8f9d0dfb941d598e843)

[AriehSchneier]

Do you have the repo rather than the worktree? If so you could try (untested code written here):

	to = object.NewTreeRootNode(t)

	idx, err := repo.Storer.Index()
	if err != nil {
		return nil, err
	}
	// mindex is utils/merkletrie/index
	from := mindex.NewRootNode(idx)

	changes, err := merkletrie.DiffTree(from, to, diffTreeIsEquals)

[aslakhellesoy]

Thanks @AriehSchneier - that seems to work. If I understand correctly, the from object here represents the staging area, right? Similar to git diff --cached?

Do you know if it would be possible to make from represent the working directory instead?

I'm trying to get the diff between a commit (HEAD) and the working directory (where some files might not be added to staging yet).

[AriehSchneier]

Ah yeh, thats correct. I think what you are after is this function:

go-git/worktree_status.go

Line 50 in dd4e2b7

func (w *Worktree) status(commit plumbing.Hash) (Status, error) {

Depending on what you are after, you could either propose a change that exposes that function (probably just needs a clearer name and then can call directly into it), or you could try copy the code locally.

PS my code snippet above came from diffTreeWithStaging

[AriehSchneier]

Oh, I missed that the commit you are trying to compare is HEAD! w.Status() should do that:

go-git/worktree_status.go

Line 35 in dd4e2b7

func (w *Worktree) Status() (Status, error) {

[aslakhellesoy]

Yeah, I had a hunch I might have to use w.Status(). Unfortunately it's too slow for me (ref #181) - I have the black hole that is node_modules 😱

Looks like I'll have to shell out to git status --porcelain --untracked-files=no instead.

[AriehSchneier]

I had a super quick look, it does the entire diff without taking into account untracked files, only afterwards does it then filter them out, hence why you are finding it slow with lots of untracked files...

[bluebrown]

I am looking for to ignore whitespace changes. With git CLI, this seems to work

git diff --ignore-blank-lines --ignore-all-space --ignore-cr-at-eol --stat

Is there a way to do it with this go module?