Fix compare dropdown for branches without common history

modules/gitrepo/compare_test.go

@@ -4,9 +4,17 @@
 package gitrepo
 
 import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
 	"testing"
+	"time"
+
+	"code.gitea.io/gitea/modules/git/gitcmd"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 type mockRepository struct {
@@ -17,6 +25,61 @@ func (r *mockRepository) RelativePath() string {
 	return r.path
 }
 
+func commitRootTree(t *testing.T, repoDir, fileName, content, message string) string {
+	t.Helper()
+
+	require.NoError(t, gitcmd.NewCommand("read-tree", "--empty").WithDir(repoDir).Run(t.Context()))
+
+	stdout, _, err := gitcmd.NewCommand("hash-object", "-w", "--stdin").
+		WithDir(repoDir).
+		WithStdinBytes([]byte(content)).
+		RunStdString(t.Context())
+	require.NoError(t, err)
+	blobSHA := strings.TrimSpace(stdout)
+
+	_, _, err = gitcmd.NewCommand("update-index", "--add", "--replace", "--cacheinfo").
+		AddDynamicArguments("100644", blobSHA, fileName).
+		WithDir(repoDir).
+		RunStdString(t.Context())
+	require.NoError(t, err)
+
+	stdout, _, err = gitcmd.NewCommand("write-tree").WithDir(repoDir).RunStdString(t.Context())
+	require.NoError(t, err)
+	treeSHA := strings.TrimSpace(stdout)
+
+	commitTimeStr := time.Now().Format(time.RFC3339)
+	env := append(os.Environ(),
+		"GIT_AUTHOR_NAME=Test",
+		"GIT_AUTHOR_EMAIL=test@example.com",
+		"GIT_AUTHOR_DATE="+commitTimeStr,
+		"GIT_COMMITTER_NAME=Test",
+		"GIT_COMMITTER_EMAIL=test@example.com",
+		"GIT_COMMITTER_DATE="+commitTimeStr,
+	)
+
+	messageBytes := bytes.NewBufferString(message + "\n")
+	stdout, _, err = gitcmd.NewCommand("commit-tree").AddDynamicArguments(treeSHA).
+		WithEnv(env).
+		WithDir(repoDir).
+		WithStdinBytes(messageBytes.Bytes()).
+		RunStdString(t.Context())
+	require.NoError(t, err)
+
+	return strings.TrimSpace(stdout)
+}
+
+func TestMergeBaseNoCommonHistory(t *testing.T) {
+	repoDir := filepath.Join(t.TempDir(), "repo.git")
+	require.NoError(t, gitcmd.NewCommand("init").AddDynamicArguments(repoDir).Run(t.Context()))
+
+	baseCommit := commitRootTree(t, repoDir, "base.txt", "base", "base")
+	headCommit := commitRootTree(t, repoDir, "head.txt", "head", "head")
+
+	mergeBase, err := MergeBase(t.Context(), &mockRepository{path: repoDir}, baseCommit, headCommit)
+	assert.Empty(t, mergeBase)
+	assert.True(t, IsErrNoMergeBase(err), "expected no merge base error, got %v", err)
+}
+
 func TestRepoGetDivergingCommits(t *testing.T) {
 	repo := &mockRepository{path: "repo1_bare"}
 	do, err := GetDivergingCommits(t.Context(), repo, "master", "branch2")

modules/gitrepo/merge.go

@@ -5,17 +5,44 @@ package gitrepo
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 
 	"code.gitea.io/gitea/modules/git/gitcmd"
 )
 
+type ErrNoMergeBase struct {
+	BaseCommitID string
+	HeadCommitID string
+	Err          error
+}
+
+func IsErrNoMergeBase(err error) bool {
+	var noMergeBase ErrNoMergeBase
+	return errors.As(err, &noMergeBase)
+}
+
+func (err ErrNoMergeBase) Error() string {
+	return fmt.Sprintf("get merge-base of %s and %s failed: %v", err.BaseCommitID, err.HeadCommitID, err.Err)
+}
+
+func (err ErrNoMergeBase) Unwrap() error {
+	return err.Err
+}
+
 // MergeBase checks and returns merge base of two commits.
 func MergeBase(ctx context.Context, repo Repository, baseCommitID, headCommitID string) (string, error) {
 	mergeBase, _, err := RunCmdString(ctx, repo, gitcmd.NewCommand("merge-base").
 		AddDashesAndList(baseCommitID, headCommitID))
 	if err != nil {
+		if gitcmd.IsErrorExitCode(err, 1) {
+			return "", ErrNoMergeBase{
+				BaseCommitID: baseCommitID,
+				HeadCommitID: headCommitID,
+				Err:          err,
+			}
+		}
 		return "", fmt.Errorf("get merge-base of %s and %s failed: %w", baseCommitID, headCommitID, err)
 	}
 	return strings.TrimSpace(mergeBase), nil

options/locale/locale_en-US.json

@@ -1784,6 +1784,7 @@
   "repo.pulls.review_only_possible_for_full_diff": "Review is only possible when viewing the full diff",
   "repo.pulls.filter_changes_by_commit": "Filter by commit",
   "repo.pulls.nothing_to_compare": "These branches are equal. There is no need to create a pull request.",
+  "repo.pulls.no_common_history": "These branches do not share a common merge base. Select a different base or compare branch.",
   "repo.pulls.nothing_to_compare_have_tag": "The selected branches/tags are equal.",
   "repo.pulls.nothing_to_compare_and_allow_empty_pr": "These branches are equal. This PR will be empty.",
   "repo.pulls.has_pull_request": "A pull request between these branches already exists: <a href=\"%[1]s\">%[2]s#%[3]d</a>",

routers/web/repo/compare.go

@@ -413,6 +413,12 @@ func ParseCompareInfo(ctx *context.Context) *git_service.CompareInfo {
 
 	compareInfo, err := git_service.GetCompareInfo(ctx, baseRepo, headRepo, headGitRepo, baseRef, headRef, compareReq.DirectComparison(), fileOnly)
 	if err != nil {
+		if gitrepo.IsErrNoMergeBase(err) {
+			ctx.Data["NoMergeBase"] = true
+			ctx.Data["BeforeCommitID"] = compareInfo.BaseCommitID
+			ctx.Data["AfterCommitID"] = compareInfo.HeadCommitID
+			return &compareInfo
+		}
 		ctx.ServerError("GetCompareInfo", err)
 		return nil
 	}
@@ -473,6 +479,12 @@ func PrepareCompareDiff(
 	ctx.Data["TitleQuery"] = newPrFormTitle
 	ctx.Data["BodyQuery"] = newPrFormBody
 
+	if ctx.Data["NoMergeBase"] == true {
+		ctx.Data["CommitCount"] = 0
+		ctx.Data["Commits"] = []*git_model.SignCommitWithStatuses{}
+		return true
+	}
+
 	if (headCommitID == ci.MergeBase && !ci.DirectComparison()) ||
 		headCommitID == ci.BaseCommitID {
 		ctx.Data["IsNothingToCompare"] = true

templates/repo/diff/compare.tmpl

@@ -168,7 +168,11 @@
 		</div>
 
 		{{$showDiffBox := and .CommitCount (not .IsNothingToCompare)}}
-		{{if and .IsSigned .PageIsComparePull}}
+		{{if .NoMergeBase}}
+			<div class="ui warning message">
+				{{ctx.Locale.Tr "repo.pulls.no_common_history"}}
+			</div>
+		{{else if and .IsSigned .PageIsComparePull}}
 			{{$allowCreatePR := and ($.CompareInfo.BaseRef.IsBranch) ($.CompareInfo.HeadRef.IsBranch) (not $.CompareInfo.DirectComparison) (or $.AllowEmptyPr (not .IsNothingToCompare))}}
 			{{if .IsNothingToCompare}}
 				<div class="ui segment">

tests/integration/compare_test.go

@@ -4,19 +4,25 @@
 package integration
 
 import (
+	"bytes"
 	"fmt"
 	"net/http"
 	"net/url"
+	"os"
 	"strings"
 	"testing"
+	"time"
 
+	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/git/gitcmd"
 	"code.gitea.io/gitea/modules/test"
 	repo_service "code.gitea.io/gitea/services/repository"
 	"code.gitea.io/gitea/tests"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestCompareTag(t *testing.T) {
@@ -124,6 +130,76 @@ func TestCompareBranches(t *testing.T) {
 	inspectCompare(t, htmlDoc, diffCount, diffChanges)
 }
 
+func createUnrelatedBranch(t *testing.T, repo *repo_model.Repository, user *user_model.User, branchName string) {
+	t.Helper()
+
+	repoPath := repo_model.RepoPath(user.Name, repo.Name)
+	require.NoError(t, gitcmd.NewCommand("read-tree", "--empty").WithDir(repoPath).Run(t.Context()))
+
+	stdout, _, err := gitcmd.NewCommand("hash-object", "-w", "--stdin").
+		WithDir(repoPath).
+		WithStdinBytes([]byte("Unrelated File")).
+		RunStdString(t.Context())
+	require.NoError(t, err)
+	blobSHA := strings.TrimSpace(stdout)
+
+	_, _, err = gitcmd.NewCommand("update-index", "--add", "--replace", "--cacheinfo").
+		AddDynamicArguments("100644", blobSHA, "unrelated.txt").
+		WithDir(repoPath).
+		RunStdString(t.Context())
+	require.NoError(t, err)
+
+	stdout, _, err = gitcmd.NewCommand("write-tree").WithDir(repoPath).RunStdString(t.Context())
+	require.NoError(t, err)
+	treeSHA := strings.TrimSpace(stdout)
+
+	commitTimeStr := time.Now().Format(time.RFC3339)
+	doerSig := user.NewGitSig()
+	env := append(os.Environ(),
+		"GIT_AUTHOR_NAME="+doerSig.Name,
+		"GIT_AUTHOR_EMAIL="+doerSig.Email,
+		"GIT_AUTHOR_DATE="+commitTimeStr,
+		"GIT_COMMITTER_NAME="+doerSig.Name,
+		"GIT_COMMITTER_EMAIL="+doerSig.Email,
+		"GIT_COMMITTER_DATE="+commitTimeStr,
+	)
+
+	messageBytes := bytes.NewBufferString("Unrelated\n")
+	stdout, _, err = gitcmd.NewCommand("commit-tree").AddDynamicArguments(treeSHA).
+		WithEnv(env).
+		WithDir(repoPath).
+		WithStdinBytes(messageBytes.Bytes()).
+		RunStdString(t.Context())
+	require.NoError(t, err)
+	commitSHA := strings.TrimSpace(stdout)
+
+	_, _, err = gitcmd.NewCommand("branch").AddDynamicArguments(branchName, commitSHA).
+		WithDir(repoPath).
+		RunStdString(t.Context())
+	require.NoError(t, err)
+}
+
+func TestCompareBranchesNoCommonMergeBase(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	user2 := unittest.AssertExistsAndLoadBean(t, &user_model.User{Name: "user2"})
+	repo1 := unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{OwnerID: user2.ID, Name: "repo1"})
+	createUnrelatedBranch(t, repo1, user2, "unrelated-history")
+
+	session := loginUser(t, "user2")
+	req := NewRequest(t, "GET", "/user2/repo1/compare/master...unrelated-history")
+	resp := session.MakeRequest(t, req, http.StatusOK)
+	body := resp.Body.String()
+	htmlDoc := NewHTMLParser(t, resp.Body)
+
+	selection := htmlDoc.doc.Find(".ui.dropdown.select-branch")
+	assert.Lenf(t, selection.Nodes, 2, "The template has changed")
+	assert.Contains(t, body, "These branches do not share a common merge base")
+	assert.Equal(t, 1, htmlDoc.doc.Find(`a.item[href="/user2/repo1/compare/master...unrelated-history"]`).Length())
+	assert.Equal(t, 1, htmlDoc.doc.Find(`a.item[href="/user2/repo1/compare/master...master"]`).Length())
+	assert.Equal(t, 0, htmlDoc.doc.Find(".pullrequest-form").Length())
+}
+
 func TestCompareCodeExpand(t *testing.T) {
 	onGiteaRun(t, func(t *testing.T, u *url.URL) {
 		user1 := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})