feat: Add diff view

Adds a very simple diff view for a commit

3 files changed, 64 insertions, 0 deletions

diff --git a/pkg/git/git.go b/pkg/git/git.go
index a9c42ce..6221e33 100644
--- a/pkg/git/git.go
+++ b/pkg/git/git.go
@@ -179,6 +179,45 @@ func (g *GitRepository) Branches() ([]*plumbing.Reference, error) {
 	return branches, nil
 }
 
+func (g *GitRepository) Diff() (string, error) {
+	err := g.validateRef()
+	if err != nil {
+		return "", err
+	}
+
+	c, err := g.repository.CommitObject(g.ref)
+	if err != nil {
+		return "", err
+	}
+
+	commitTree, err := c.Tree()
+	if err != nil {
+		return "", err
+	}
+
+	patch := &object.Patch{}
+	parentTree := &object.Tree{}
+	if c.NumParents() != 0 {
+		parent, err := c.Parents().Next()
+		if err == nil {
+			parentTree, err = parent.Tree()
+			if err == nil {
+				patch, err = parentTree.Patch(commitTree)
+				if err != nil {
+					return "", err
+				}
+			}
+		}
+	} else {
+		patch, err = parentTree.Patch(commitTree)
+		if err != nil {
+			return "", err
+		}
+	}
+
+	return patch.String(), nil
+}
+
 func (g *GitRepository) Tree(path string) (*object.Tree, error) {
 	err := g.validateRef()
 	if err != nil {
diff --git a/pkg/handler/git/handler.go b/pkg/handler/git/handler.go
index 2ddc5f1..40fae24 100644
--- a/pkg/handler/git/handler.go
+++ b/pkg/handler/git/handler.go
@@ -340,11 +340,17 @@ func (g *GitHandler) Commit(w http.ResponseWriter, r *http.Request) error {
 		return err
 	}
 
+	diff, err := g.gitService.Diff(name, ref)
+	if err != nil {
+		return err
+	}
+
 	gitList := &templates.GitItemPage{
 		Name: name,
 		Ref:  ref,
 		GitItemBase: &templates.GitItemCommitPage{
 			Commit: commit,
+			Diff:   diff,
 		},
 	}
 	templates.WritePageTemplate(w, gitList)
diff --git a/pkg/service/git.go b/pkg/service/git.go
index b368f0c..f03ba42 100644
--- a/pkg/service/git.go
+++ b/pkg/service/git.go
@@ -140,6 +140,25 @@ func (g *GitService) WriteTarGZip(w io.Writer, name, ref string, prefix string)
 	return nil
 }
 
+func (g *GitService) Diff(name, ref string) (string, error) {
+	r := g.configRepo.GetByName(name)
+	if r == nil {
+		return "", ErrRepositoryNotFound
+	}
+
+	repo, err := git.OpenRepository(r.Path)
+	if err != nil {
+		return "", err
+	}
+
+	err = repo.SetRef(ref)
+	if err != nil {
+		return "", err
+	}
+
+	return repo.Diff()
+}
+
 func (g *GitService) GetTree(name, ref, path string) (*object.Tree, error) {
 	r := g.configRepo.GetByName(name)
 	if r == nil {