knotserver: git: remove MergeBase calculation

the rev-list approach to building format-patch internally performs
merge-base calculations.

Signed-off-by: oppiliappan <[e-mail]>

knotserver/git/diff.go

···
 	return stdout.String(), &formatPatch[0], nil
 }
 
-func (g *GitRepo) MergeBase(commit1, commit2 *object.Commit) (*object.Commit, error) {
-	isAncestor, err := commit1.IsAncestor(commit2)
-	if err != nil {
-		return nil, err
-	}
-
-	if isAncestor {
-		return commit1, nil
-	}
-
-	mergeBase, err := commit1.MergeBase(commit2)
-	if err != nil {
-		return nil, err
-	}
-
-	if len(mergeBase) == 0 {
-		return nil, fmt.Errorf("failed to find a merge-base")
-	}
-
-	return mergeBase[0], nil
-}
-
 func (g *GitRepo) ResolveRevision(revStr string) (*object.Commit, error) {
 	rev, err := g.r.ResolveRevision(plumbing.Revision(revStr))
 	if err != nil {
···
 		if err != nil {
 			continue
 		}
-
 		commits = append(commits, obj)
 	}
 
···
 }
 
 func (g *GitRepo) FormatPatch(base, commit2 *object.Commit) (string, []types.FormatPatch, error) {
-	// get list of commits between commir2 and base
+	// get list of commits between commit2 and base
 	commits, err := g.commitsBetween(commit2, base)
 	if err != nil {
 		return "", nil, fmt.Errorf("failed to get commits: %w", err)

knotserver/routes.go

···
 		return
 	}
 
-	mergeBase, err := gr.MergeBase(commit1, commit2)
-	if err != nil {
-		l.Error("failed to find merge-base", "msg", err.Error())
-		writeError(w, "failed to calculate diff", http.StatusBadRequest)
-		return
-	}
-
-	rawPatch, formatPatch, err := gr.FormatPatch(mergeBase, commit2)
+	rawPatch, formatPatch, err := gr.FormatPatch(commit1, commit2)
 	if err != nil {
 		l.Error("error comparing revisions", "msg", err.Error())
 		writeError(w, "error comparing revisions", http.StatusBadRequest)
···
 		Rev1:        commit1.Hash.String(),
 		Rev2:        commit2.Hash.String(),
 		FormatPatch: formatPatch,
-		MergeBase:   mergeBase.Hash.String(),
 		Patch:       rawPatch,
 	})
 	return

types/repo.go

···
 	Rev1        string        `json:"rev1,omitempty"`
 	Rev2        string        `json:"rev2,omitempty"`
 	FormatPatch []FormatPatch `json:"format_patch,omitempty"`
-	MergeBase   string        `json:"merge_base,omitempty"`
+	MergeBase   string        `json:"merge_base,omitempty"` // deprecated
 	Patch       string        `json:"patch,omitempty"`
 }