fix: pass merge commit messages to git via stdin (#39269)

`git commit --message=` passes the merge message as a single argument,
which Linux caps at 128 KiB and Windows at 32 KiB for the whole command
line. Long messages failed with `argument list too long` and the merge
box toast showed the raw HTML 500 page.

Pass the message via `--file=-` on stdin instead, and answer
fetch-action requests with JSON on server errors so the toast shows the
error text. Limits merge commit messages to 512KB which could be
extended or made configurable later.

Fixes: https://github.com/go-gitea/gitea/issues/39261
Fixes: https://github.com/go-gitea/gitea/issues/30276
Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/git/commit.go

@@ -248,3 +248,14 @@ func GetFullCommitID(ctx context.Context, repo RepositoryFacade, shortID string)
 	}
 	return strings.TrimSpace(commitID), nil
 }
+
+func AddObjectMessageArgument(cmd *gitcmd.Command, typ ObjectType, message string) error {
+	if len(message) > 512*1024 {
+		// It doesn't make sense to store very large messages in git objects,
+		// and it never succeeded in the past due to the command line argument limit (e.g.: 128K on Linux).
+		// If any real world user would complain about the limit, let them explain why, then make the limit configurable.
+		return util.NewInvalidArgumentErrorf("git %s message is too long", typ)
+	}
+	cmd.AddArguments("--file=-").WithStdinBytes([]byte(message))
+	return nil
+}

modules/git/gitcmd/pipe.go

@@ -8,11 +8,6 @@ import (
 	"os"
 )
 
-type PipeBufferReader interface {
-	Read(p []byte) (n int, err error)
-	Bytes() []byte
-}
-
 type PipeBufferWriter interface {
 	Write(p []byte) (n int, err error)
 	Bytes() []byte

modules/git/repo_commit_nogogit.go

@@ -9,32 +9,10 @@ import (
 	"context"
 	"errors"
 	"io"
-	"strings"
 
-	"gitea.dev/modules/git/gitcmd"
-	"gitea.dev/modules/log"
+	"gitea.dev/modules/setting"
 )
 
-// ResolveReference resolves a name to a reference
-func (repo *Repository) ResolveReference(ctx context.Context, name string) (string, error) {
-	stdout, _, err := gitcmd.NewCommand("show-ref", "--hash").
-		AddDynamicArguments(name).
-		WithRepo(repo).
-		RunStdString(ctx)
-	if err != nil {
-		if strings.Contains(err.Error(), "not a valid ref") {
-			return "", ErrNotExist{name, ""}
-		}
-		return "", err
-	}
-	stdout = strings.TrimSpace(stdout)
-	if stdout == "" {
-		return "", ErrNotExist{name, ""}
-	}
-
-	return stdout, nil
-}
-
 // GetRefCommitID returns the last commit ID string of given reference (branch or tag).
 func (repo *Repository) GetRefCommitID(ctx context.Context, name string) (string, error) {
 	batch, cancel, err := repo.CatFileBatch()
@@ -60,6 +38,15 @@ func (repo *Repository) getCommit(ctx context.Context, id ObjectID) (*Commit, er
 	return repo.getCommitWithBatch(batch, id)
 }
 
+func limitDiscardReader(rd BufferedReader, full, limit int64) (io.Reader, func() error) {
+	return io.LimitReader(rd, min(full, limit)), func() error {
+		if full > limit {
+			return DiscardFull(rd, full-limit)
+		}
+		return nil
+	}
+}
+
 func (repo *Repository) getCommitWithBatch(batch CatFileBatch, id ObjectID) (*Commit, error) {
 	info, rd, err := batch.QueryContent(id.String())
 	if err != nil {
@@ -73,12 +60,14 @@ func (repo *Repository) getCommitWithBatch(batch CatFileBatch, id ObjectID) (*Co
 	case "missing":
 		return nil, ErrNotExist{ID: id.String()}
 	case "tag":
-		// then we need to parse the tag
-		// and load the commit
-		data, err := io.ReadAll(io.LimitReader(rd, info.Size))
+		limitReader, limitDiscard := limitDiscardReader(rd, info.Size, MaxGitObjectSize)
+		data, err := io.ReadAll(limitReader)
 		if err != nil {
 			return nil, err
 		}
+		if err = limitDiscard(); err != nil {
+			return nil, err
+		}
 		_, err = rd.Discard(1)
 		if err != nil {
 			return nil, err
@@ -89,10 +78,14 @@ func (repo *Repository) getCommitWithBatch(batch CatFileBatch, id ObjectID) (*Co
 		}
 		return repo.getCommitWithBatch(batch, tag.Object)
 	case "commit":
-		commit, err := CommitFromReader(id, io.LimitReader(rd, info.Size))
+		limitReader, limitDiscard := limitDiscardReader(rd, info.Size, MaxGitObjectSize)
+		commit, err := CommitFromReader(id, limitReader)
 		if err != nil {
 			return nil, err
 		}
+		if err = limitDiscard(); err != nil {
+			return nil, err
+		}
 		_, err = rd.Discard(1)
 		if err != nil {
 			return nil, err
@@ -100,7 +93,9 @@ func (repo *Repository) getCommitWithBatch(batch CatFileBatch, id ObjectID) (*Co
 
 		return commit, nil
 	default:
-		log.Debug("Unknown cat-file object type: %s", info.Type)
+		if info.Type != "blob" && info.Type != "tree" {
+			setting.PanicInDevOrTesting("Unknown cat-file object type %s for object %s in repo %s", info.Type, id.String(), repo.LogString())
+		}
 		if err := DiscardFull(rd, info.Size+1); err != nil {
 			return nil, err
 		}

modules/git/repo_index.go

@@ -73,12 +73,6 @@ func (repo *Repository) ReadTreeToTemporaryIndex(ctx context.Context, treeish st
 	return tmpIndexFilename, tmpDir, cancel, nil
 }
 
-// EmptyIndex empties the index
-func (repo *Repository) EmptyIndex(ctx context.Context) error {
-	_, _, err := gitcmd.NewCommand("read-tree", "--empty").WithRepo(repo).RunStdString(ctx)
-	return err
-}
-
 // LsFiles checks if the given filenames are in the index
 func (repo *Repository) LsFiles(ctx context.Context, filenames ...string) ([]string, error) {
 	cmd := gitcmd.NewCommand("ls-files", "-z").AddDashesAndList(filenames...)

modules/git/repo_object.go

@@ -11,6 +11,10 @@ import (
 	"gitea.dev/modules/git/gitcmd"
 )
 
+// MaxGitObjectSize is used to avoid OOM when reading a large git object.
+// GitHub has a limit (100M) for pushing, but Gitea doesn't have such a limit yet.
+var MaxGitObjectSize int64 = 100 * 1024 * 1024
+
 // ObjectType git object type
 type ObjectType string
 

modules/git/repo_tag.go

@@ -27,11 +27,11 @@ func (repo *Repository) CreateTag(ctx context.Context, name, revision string) er
 
 // CreateAnnotatedTag create one annotated tag in the repository
 func (repo *Repository) CreateAnnotatedTag(ctx context.Context, name, message, revision string) error {
-	_, _, err := gitcmd.NewCommand("tag", "-a", "-m").
-		AddDynamicArguments(message).
-		AddDashesAndList(name, revision).
-		WithRepo(repo).
-		RunStdString(ctx)
+	cmd := gitcmd.NewCommand("tag", "--annotate")
+	if err := AddObjectMessageArgument(cmd, ObjectTag, message); err != nil {
+		return err
+	}
+	_, _, err := cmd.AddDashesAndList(name, revision).WithRepo(repo).RunStdString(ctx)
 	return err
 }
 

modules/git/repo_tag_nogogit.go

@@ -106,12 +106,15 @@ func (repo *Repository) getTag(ctx context.Context, tagID ObjectID, name string)
 		return nil, ErrNotExist{ID: tagID.String()}
 	}
 
-	// then we need to parse the tag
-	// and load the commit
-	data, err := io.ReadAll(io.LimitReader(rd, size))
+	// then we need to parse the tag and load the commit
+	limitReader, limitDiscard := limitDiscardReader(rd, info.Size, MaxGitObjectSize)
+	data, err := io.ReadAll(limitReader)
 	if err != nil {
 		return nil, err
 	}
+	if err = limitDiscard(); err != nil {
+		return nil, err
+	}
 	_, err = rd.Discard(1)
 	if err != nil {
 		return nil, err

modules/httplib/server_request.go

@@ -5,6 +5,8 @@ package httplib
 
 import (
 	"context"
+	"errors"
+	"io"
 	"net"
 	"net/http"
 	"net/url"
@@ -240,3 +242,28 @@ func ParseGiteaSiteURL(ctx context.Context, s string) *GiteaSiteURL {
 	}
 	return ret
 }
+
+func IsGiteaFetchActionRequest(req *http.Request) bool {
+	return req.Header.Get("X-Gitea-Fetch-Action") != ""
+}
+
+func IsClientOrNetworkError(ctx context.Context, err error) bool {
+	if err == nil {
+		return false
+	}
+
+	if ctx.Err() != nil || errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+		return true
+	}
+
+	// client request corrupted (e.g.: Content-Length is sent but body is incomplete)
+	if errors.Is(err, io.ErrUnexpectedEOF) {
+		return true
+	}
+
+	// network error
+	if _, ok := errors.AsType[net.Error](err); ok {
+		return true
+	}
+	return false
+}

modules/web/middleware/cookie.go

@@ -9,6 +9,7 @@ import (
 	"net/url"
 	"strings"
 
+	"gitea.dev/modules/httplib"
 	"gitea.dev/modules/session"
 	"gitea.dev/modules/setting"
 	"gitea.dev/modules/util"
@@ -35,7 +36,7 @@ func DeleteRedirectToCookie(resp http.ResponseWriter) {
 }
 
 func RedirectLinkUserLogin(req *http.Request) string {
-	if req.Header.Get("X-Gitea-Fetch-Action") != "" {
+	if httplib.IsGiteaFetchActionRequest(req) {
 		// when building the redirect link for a fetch request, the current link might be a partial page,
 		// so we only redirect to the login page without redirect_to parameter
 		return setting.AppSubURL + "/user/login"

services/context/base.go

@@ -161,7 +161,7 @@ func (b *Base) Redirect(location string, status ...int) {
 	}
 	// In case the request is made by "fetch-action" module, make JS redirect to the new location
 	// Otherwise, the JS fetch will follow the redirection and read a "login" page, embed it to the current page, which is not expected.
-	if b.Req.Header.Get("X-Gitea-Fetch-Action") != "" {
+	if httplib.IsGiteaFetchActionRequest(b.Req) {
 		b.JSON(http.StatusOK, map[string]any{"redirect": location})
 		return
 	}

services/context/base_test.go

@@ -6,6 +6,7 @@ package context
 import (
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"testing"
 
 	"gitea.dev/modules/setting"
@@ -13,8 +14,12 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestRedirect(t *testing.T) {
+func TestMain(m *testing.M) {
 	setting.IsInTesting = true
+	os.Exit(m.Run())
+}
+
+func TestRedirect(t *testing.T) {
 	req, _ := http.NewRequest(http.MethodGet, "/", nil)
 
 	cases := []struct {

services/context/context.go

@@ -270,8 +270,12 @@ func (ctx *Context) JSONErrorAuto(err error) {
 		ctx.JSON(httpCode, buildJsonErrorMap(errMsg))
 		return
 	}
-	log.ErrorWithSkip(1, "JSONErrorAuto: server internal error: %v", err)
-	ctx.JSON(http.StatusInternalServerError, buildJsonErrorMap(ctx.Locale.TrString("error.occurred")))
+
+	logLevel := util.Iif(httplib.IsClientOrNetworkError(ctx, err), log.DEBUG, log.ERROR)
+	log.Log(1, logLevel, "JSONErrorAuto: server internal error: %v", err)
+
+	userErrorMsg := ctx.buildUserErrorMessage("internal server error", err)
+	ctx.JSON(http.StatusInternalServerError, buildJsonErrorMap(userErrorMsg))
 }
 
 func (ctx *Context) JSONError[T string | template.HTML](msg T) {

services/context/context_response.go

@@ -7,13 +7,11 @@ import (
 	"errors"
 	"fmt"
 	"html/template"
-	"net"
 	"net/http"
 	"net/url"
 	"path"
 	"strconv"
 	"strings"
-	"syscall"
 	"time"
 
 	user_model "gitea.dev/models/user"
@@ -90,7 +88,7 @@ func (ctx *Context) HTML(status int, name templates.TplName) {
 	}
 
 	err := ctx.Render.HTML(ctx.Resp, status, name, ctx.Data, ctx.TemplateContext)
-	if err == nil || errors.Is(err, syscall.EPIPE) {
+	if err == nil || httplib.IsClientOrNetworkError(ctx, err) {
 		return
 	}
 
@@ -126,13 +124,13 @@ func (ctx *Context) RenderWithErrDeprecated(msg any, tpl templates.TplName, form
 
 // NotFound displays a 404 (Not Found) page and prints the given error, if any.
 func (ctx *Context) NotFound(logErr error) {
-	ctx.notFoundInternal("", logErr)
+	ctx.notFoundInternal(1, "", logErr)
 }
 
-func (ctx *Context) notFoundInternal(logMsg string, logErr error) {
+func (ctx *Context) notFoundInternal(skip int, logMsg string, logErr error) {
 	// TODO: it's safe to show the error message to end users if the error is fully controlled by our error system
 	if logErr != nil {
-		log.Log(2, log.DEBUG, "%s: %v", logMsg, logErr)
+		log.Log(skip+1, log.DEBUG, "%s: %v", logMsg, logErr)
 	}
 
 	// response simple message if Accept isn't text/html
@@ -155,32 +153,41 @@ func (ctx *Context) notFoundInternal(logMsg string, logErr error) {
 	ctx.HTML(http.StatusNotFound, "status/404")
 }
 
+func (ctx *Context) buildUserErrorMessage(msg string, err error) (userErrorMsg string) {
+	// it's safe to show internal error to admin users, and it helps
+	if !setting.IsProd || (ctx.Doer != nil && ctx.Doer.IsAdmin) {
+		userErrorMsg = msg
+		if err != nil {
+			userErrorMsg += ", error: " + err.Error()
+		}
+	}
+	return util.IfZero(userErrorMsg, ctx.Locale.TrString("error.occurred"))
+}
+
 // ServerError displays a 500 (Internal Server Error) page and prints the given error, if any.
 // If the error is controlled by our error system, a related 404 page can be displayed instead.
 func (ctx *Context) ServerError(logMsg string, logErr error) {
 	if errors.Is(logErr, util.ErrNotExist) {
-		ctx.notFoundInternal(logMsg, logErr)
+		ctx.notFoundInternal(1, logMsg, logErr)
 		return
 	}
-	ctx.serverErrorInternal(logMsg, logErr)
+	ctx.serverErrorInternal(1, logMsg, logErr)
 }
 
-func (ctx *Context) serverErrorInternal(logMsg string, logErr error) {
+func (ctx *Context) serverErrorInternal(skip int, logMsg string, logErr error) {
 	if logErr != nil {
-		log.ErrorWithSkip(2, "%s: %v", logMsg, logErr)
-		if _, ok := logErr.(*net.OpError); ok || errors.Is(logErr, &net.OpError{}) {
-			// This is an error within the underlying connection
-			// and further rendering will not work so just return
-			return
-		}
+		logLevel := util.Iif(httplib.IsClientOrNetworkError(ctx, logErr), log.DEBUG, log.ERROR)
+		log.Log(skip+1, logLevel, "%s: %v", logMsg, logErr)
+	}
 
-		// it's safe to show internal error to admin users, and it helps
-		if !setting.IsProd || (ctx.Doer != nil && ctx.Doer.IsAdmin) {
-			ctx.Data["ErrorMsg"] = fmt.Sprintf("%s, %s", logMsg, logErr)
-		}
+	userErrorMsg := ctx.buildUserErrorMessage(logMsg, logErr)
+	if httplib.IsGiteaFetchActionRequest(ctx.Req) {
+		ctx.JSON(http.StatusInternalServerError, buildJsonErrorMap(userErrorMsg))
+		return
 	}
 
 	ctx.Data["Title"] = "Internal Server Error"
+	ctx.Data["ErrorMsg"] = userErrorMsg
 	ctx.HTML(http.StatusInternalServerError, tplStatus500)
 }
 
@@ -190,8 +197,8 @@ func (ctx *Context) serverErrorInternal(logMsg string, logErr error) {
 // TODO: remove the "errCheck" and use util.ErrNotFound to check
 func (ctx *Context) NotFoundOrServerError(logMsg string, errCheck func(error) bool, logErr error) {
 	if errCheck(logErr) {
-		ctx.notFoundInternal(logMsg, logErr)
+		ctx.notFoundInternal(1, logMsg, logErr)
 		return
 	}
-	ctx.serverErrorInternal(logMsg, logErr)
+	ctx.serverErrorInternal(1, logMsg, logErr)
 }

services/context/context_test.go

@@ -4,6 +4,7 @@
 package context
 
 import (
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -27,8 +28,18 @@ func TestRemoveSessionCookieHeader(t *testing.T) {
 	assert.Contains(t, "other=bar", w.Header().Get("Set-Cookie"))
 }
 
+func TestServerErrorFetchActionRespondsJSON(t *testing.T) {
+	req, _ := http.NewRequest(http.MethodPost, "/", nil)
+	req.Header.Add("X-Gitea-Fetch-Action", "1")
+	resp := httptest.NewRecorder()
+	ctx := NewWebContext(NewBaseContextForTest(t, resp, req), nil, nil)
+	ctx.ServerError("test", errors.New("boom"))
+	assert.Equal(t, http.StatusInternalServerError, resp.Code)
+	assert.Contains(t, resp.Header().Get("Content-Type"), "application/json")
+	assert.JSONEq(t, `{"errorMessage":"test, error: boom","renderFormat":"text"}`, resp.Body.String())
+}
+
 func TestRedirectToCurrentSite(t *testing.T) {
-	setting.IsInTesting = true
 	defer test.MockVariableValue(&setting.AppURL, "http://localhost:3000/sub/")()
 	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
 	cases := []struct {
@@ -53,7 +64,6 @@ func TestRedirectToCurrentSite(t *testing.T) {
 }
 
 func TestAppFullLink(t *testing.T) {
-	setting.IsInTesting = true
 	defer test.MockVariableValue(&setting.AppURL, "https://gitea.example.com/sub/")()
 	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
 	defer test.MockVariableValue(&setting.PublicURLDetection, setting.PublicURLNever)()

services/pull/merge.go

@@ -460,7 +460,10 @@ func doMergeAndPush(ctx context.Context, pr *issues_model.PullRequest, doer *use
 }
 
 func commitAndSignNoAuthor(ctx *mergeContext, message string) error {
-	cmdCommit := gitcmd.NewCommand("commit").AddOptionFormat("--message=%s", message)
+	cmdCommit := gitcmd.NewCommand("commit")
+	if err := git.AddObjectMessageArgument(cmdCommit, git.ObjectCommit, message); err != nil {
+		return err
+	}
 	addCommitSigningOptions(cmdCommit, ctx.signKey)
 	if err := ctx.PrepareGitCmd(cmdCommit).RunWithStderr(ctx); err != nil {
 		return fmt.Errorf("git commit %v: %w\n%s", ctx.pr, err, ctx.outbuf.String())

services/pull/merge_rebase.go

@@ -73,8 +73,10 @@ func doMergeRebaseFastForward(ctx *mergeContext) error {
 	}
 
 	if newMessage != "" {
-		cmdCommit := gitcmd.NewCommand("commit", "--amend").
-			AddOptionFormat("--message=%s", newMessage)
+		cmdCommit := gitcmd.NewCommand("commit", "--amend")
+		if err = git.AddObjectMessageArgument(cmdCommit, git.ObjectCommit, newMessage); err != nil {
+			return err
+		}
 		addCommitSigningOptions(cmdCommit, ctx.signKey)
 		if err := cmdCommit.WithRepo(ctx.tmpRepo).Run(ctx); err != nil {
 			log.Error("Unable to amend commit message: %v", err)

services/pull/merge_squash.go

@@ -67,10 +67,11 @@ func doMergeStyleSquash(ctx *mergeContext, message string) error {
 	if setting.Repository.PullRequest.AddCoCommitterTrailers && ctx.committer.String() != sig.String() {
 		message = AddCommitMessageTailer(message, git.CoAuthoredByTrailer, sig.String())
 	}
-	cmdCommit := gitcmd.NewCommand("commit").
-		AddOptionFormat("--author='%s <%s>'", sig.Name, sig.Email).
-		AddOptionFormat("--message=%s", message).
-		AddArguments("--allow-empty")
+	cmdCommit := gitcmd.NewCommand("commit", "--allow-empty").
+		AddOptionFormat("--author='%s <%s>'", sig.Name, sig.Email)
+	if err = git.AddObjectMessageArgument(cmdCommit, git.ObjectCommit, message); err != nil {
+		return err
+	}
 	addCommitSigningOptions(cmdCommit, ctx.signKey)
 	if err := ctx.PrepareGitCmd(cmdCommit).RunWithStderr(ctx); err != nil {
 		log.Error("git commit %-v: %v\n%s\n%s", ctx.pr, err, ctx.outbuf.String(), err.Stderr())

tests/integration/api_repo_git_tags_test.go

@@ -6,6 +6,7 @@ package integration
 import (
 	"fmt"
 	"net/http"
+	"strings"
 	"testing"
 
 	auth_model "gitea.dev/models/auth"
@@ -14,6 +15,7 @@ import (
 	user_model "gitea.dev/models/user"
 	"gitea.dev/modules/git"
 	api "gitea.dev/modules/structs"
+	"gitea.dev/modules/test"
 	"gitea.dev/tests"
 
 	"github.com/stretchr/testify/assert"
@@ -36,20 +38,17 @@ func TestAPIGitTags(t *testing.T) {
 
 	commit, _ := gitRepo.GetBranchCommit(t.Context(), "master")
 	lTagName := "lightweightTag"
-	gitRepo.CreateTag(t.Context(), lTagName, commit.ID.String())
+	_ = gitRepo.CreateTag(t.Context(), lTagName, commit.ID.String())
 
 	aTagName := "annotatedTag"
-	aTagMessage := "my annotated message"
-	gitRepo.CreateAnnotatedTag(t.Context(), aTagName, aTagMessage, commit.ID.String())
+	aTagMessage := strings.Repeat("very long " /*10bytes*/, 20*1024) + "annotated message"
+	_ = gitRepo.CreateAnnotatedTag(t.Context(), aTagName, aTagMessage, commit.ID.String())
 	aTag, _ := gitRepo.GetTag(t.Context(), aTagName)
 
 	// SHOULD work for annotated tags
-	req := NewRequestf(t, "GET", "/api/v1/repos/%s/%s/git/tags/%s", user.Name, repo.Name, aTag.ID.String()).
-		AddTokenAuth(token)
-	res := MakeRequest(t, req, http.StatusOK)
-
-	tag := DecodeJSON(t, res, &api.AnnotatedTag{})
-
+	req := NewRequestf(t, "GET", "/api/v1/repos/%s/%s/git/tags/%s", user.Name, repo.Name, aTag.ID.String()).AddTokenAuth(token)
+	resp := MakeRequest(t, req, http.StatusOK)
+	tag := DecodeJSON(t, resp, &api.AnnotatedTag{})
 	assert.Equal(t, aTagName, tag.Tag)
 	assert.Equal(t, aTag.ID.String(), tag.SHA)
 	assert.Equal(t, commit.ID.String(), tag.Object.SHA)
@@ -58,6 +57,16 @@ func TestAPIGitTags(t *testing.T) {
 	assert.Equal(t, user.Email, tag.Tagger.Email)
 	assert.Equal(t, repo.APIURL()+"/git/tags/"+aTag.ID.String(), tag.URL)
 
+	if !git.DefaultFeatures().UsingGogit {
+		defer test.MockVariableValue(&git.MaxGitObjectSize, 1024)()
+		req = NewRequestf(t, "GET", "/api/v1/repos/%s/%s/git/tags/%s", user.Name, repo.Name, aTag.ID.String()).AddTokenAuth(token)
+		resp = MakeRequest(t, req, http.StatusOK)
+		tag = DecodeJSON(t, resp, &api.AnnotatedTag{})
+		assert.True(t, strings.HasPrefix(aTagMessage, tag.Message))
+		assert.Less(t, len(tag.Message), len(aTagMessage))
+		assert.Less(t, len(tag.Message), 1024)
+	}
+
 	// Should NOT work for lightweight tags
 	badReq := NewRequestf(t, "GET", "/api/v1/repos/%s/%s/git/tags/%s", user.Name, repo.Name, commit.ID.String()).
 		AddTokenAuth(token)

tests/integration/pull_merge_test.go

@@ -51,6 +51,7 @@ type MergeOptions struct {
 	Style        repo_model.MergeStyle
 	HeadCommitID string
 	DeleteBranch bool
+	Message      string
 }
 
 func testPullMerge(t *testing.T, session *TestSession, user, repo, pullNum string, mergeOptions MergeOptions) *httptest.ResponseRecorder {
@@ -58,6 +59,7 @@ func testPullMerge(t *testing.T, session *TestSession, user, repo, pullNum strin
 		"do":                        string(mergeOptions.Style),
 		"head_commit_id":            mergeOptions.HeadCommitID,
 		"delete_branch_after_merge": util.Iif(mergeOptions.DeleteBranch, "on", ""),
+		"merge_message_field":       mergeOptions.Message,
 	}
 	var resp *httptest.ResponseRecorder
 	require.Eventually(t, func() bool {
@@ -77,6 +79,15 @@ func testPullMerge(t *testing.T, session *TestSession, user, repo, pullNum strin
 	assert.NoError(t, err)
 	assert.True(t, pull.HasMerged)
 
+	if mergeOptions.Message != "" {
+		gitRepo, err := git.OpenRepository(t.Context(), repository)
+		require.NoError(t, err)
+		defer gitRepo.Close()
+		commit, err := gitRepo.GetCommit(t.Context(), pull.MergedCommitID)
+		require.NoError(t, err)
+		assert.Contains(t, commit.CommitMessage.MessageRaw, mergeOptions.Message)
+	}
+
 	return resp
 }
 
@@ -116,8 +127,8 @@ func TestPullMerge(t *testing.T) {
 		elem := strings.Split(test.RedirectURL(resp), "/")
 		assert.Equal(t, "pulls", elem[3])
 		testPullMerge(t, session, elem[1], elem[2], elem[4], MergeOptions{
-			Style:        repo_model.MergeStyleMerge,
-			DeleteBranch: false,
+			Style:   repo_model.MergeStyleMerge,
+			Message: strings.Repeat("x", 200*1024),
 		})
 
 		repo = unittest.AssertExistsAndLoadBean(t, &repo_model.Repository{ID: repo.ID})