enhance: fall back to DEFAULT_TEMPLATE.md when style-specific template is missing (#38803)

Closes #38801

Introduce `DEFAULT_TEMPLATE.md` as the default message for all merge
styles.

https://gitea.com/gitea/docs/pulls/491

By the way, fix incorrect os.Expand usage for merge message & repo
template

---------

Co-authored-by: waterWang <waterWang@users.noreply.github.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/git/fastimport.go

@@ -7,11 +7,18 @@ import (
 	"bytes"
 	"context"
 	"fmt"
+	"os"
 
 	"gitea.dev/modules/git/gitcmd"
+	"gitea.dev/modules/git/gitrepo"
 	"gitea.dev/modules/util"
 )
 
+type FastImportInit struct {
+	Bare         bool
+	ObjectFormat string
+}
+
 type FastImportFile struct {
 	Mode    EntryMode
 	Path    string
@@ -24,6 +31,20 @@ type FastImportCommit struct {
 	Files   []FastImportFile
 }
 
+// ForceFastImportWithInit is for mainly for testing purpose
+func ForceFastImportWithInit(ctx context.Context, repoLocalPath string, commits []FastImportCommit, initOpts ...FastImportInit) (RepositoryFacade, error) {
+	repo := gitrepo.RepositoryUnmanaged(repoLocalPath)
+	initOpt := util.OptionalArg(initOpts, FastImportInit{Bare: true})
+	if exist, _ := IsRepositoryExist(ctx, repo); !exist {
+		_ = os.MkdirAll(repoLocalPath, 0o755)
+		err := InitRepositoryLocal(ctx, repoLocalPath, initOpt.Bare, util.IfZero(initOpt.ObjectFormat, "sha1"))
+		if err != nil {
+			return nil, err
+		}
+	}
+	return repo, ForceFastImport(ctx, repo, commits)
+}
+
 // ForceFastImport is for mainly for testing purpose
 func ForceFastImport(ctx context.Context, repo RepositoryFacade, commits []FastImportCommit) error {
 	var buf bytes.Buffer

modules/markup/html_issue.go

@@ -149,7 +149,7 @@ func issueIndexPatternProcessor(ctx *RenderContext, node *html.Node) {
 		if hasExtTrackFormat && !ref.IsPull {
 			ctx.RenderOptions.Metas["index"] = ref.Issue
 
-			res, err := vars.Expand(ctx.RenderOptions.Metas["format"], ctx.RenderOptions.Metas)
+			res, err := vars.ExpandCurlyBrace(ctx.RenderOptions.Metas["format"], ctx.RenderOptions.Metas)
 			if err != nil {
 				// here we could just log the error and continue the rendering
 				log.Error("unable to expand template vars for ref %s, err: %v", ref.Issue, err)

modules/templates/vars/vars.go

@@ -5,14 +5,17 @@ package vars
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
+	"sync"
 	"unicode"
 	"unicode/utf8"
 )
 
-// Expand replaces all variables like {var} by `vars` map, it always returns the expanded string regardless of errors
-// if error occurs, the error part doesn't change and is returned as it is.
-func Expand(template string, vars map[string]string) (string, error) {
+// ExpandCurlyBrace replaces all variables like {var} by `vars` map,
+// it always returns the expanded string regardless of errors.
+// if error occurs (wrong syntax, missing variable), the error part doesn't change and is returned as it is.
+func ExpandCurlyBrace(template string, vars map[string]string) (string, error) {
 	// in the future, if necessary, we can introduce some escape-char,
 	// for example: it will use `#' as a reversed char, templates will use `{#{}` to do escape and output char '{'.
 	var buf strings.Builder
@@ -71,3 +74,26 @@ func Expand(template string, vars map[string]string) (string, error) {
 
 	return buf.String(), err
 }
+
+var globalVars = sync.OnceValue(func() (ret struct {
+	regexpShellLike *regexp.Regexp
+},
+) {
+	ret.regexpShellLike = regexp.MustCompile(`(\$\{[a-zA-Z_]\w*\}|\$[a-zA-Z_]\w*)`)
+	return ret
+})
+
+// ExpandShellLike works like os.Expand, the difference is that this function keeps the non-existing keys
+func ExpandShellLike(template string, vars map[string]string) string {
+	re := globalVars().regexpShellLike
+	return re.ReplaceAllStringFunc(template, func(s string) string {
+		key := s[1:]
+		if strings.HasPrefix(key, "{") && strings.HasSuffix(key, "}") {
+			key = key[1 : len(key)-1]
+		}
+		if val, ok := vars[key]; ok {
+			return val
+		}
+		return s
+	})
+}

modules/templates/vars/vars_test.go

@@ -9,8 +9,8 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestExpandVars(t *testing.T) {
-	kases := []struct {
+func TestExpandCurlyBrace(t *testing.T) {
+	cases := []struct {
 		tmpl  string
 		data  map[string]string
 		out   string
@@ -57,11 +57,11 @@ func TestExpandVars(t *testing.T) {
 		},
 	}
 
-	for _, kase := range kases {
-		t.Run(kase.tmpl, func(t *testing.T) {
-			res, err := Expand(kase.tmpl, kase.data)
-			assert.Equal(t, kase.out, res)
-			if kase.error {
+	for _, c := range cases {
+		t.Run(c.tmpl, func(t *testing.T) {
+			res, err := ExpandCurlyBrace(c.tmpl, c.data)
+			assert.Equal(t, c.out, res)
+			if c.error {
 				assert.Error(t, err)
 			} else {
 				assert.NoError(t, err)
@@ -69,3 +69,19 @@ func TestExpandVars(t *testing.T) {
 		})
 	}
 }
+
+func TestExpandShellLike(t *testing.T) {
+	cases := []struct {
+		tmpl string
+		data map[string]string
+		out  string
+	}{
+		{tmpl: "$key ${key} $other ${other}", data: map[string]string{"key": "val"}, out: "val val $other ${other}"},
+		{tmpl: "$ key ${key }", data: map[string]string{"key": "val"}, out: "$ key ${key }"},
+	}
+
+	for _, c := range cases {
+		out := ExpandShellLike(c.tmpl, c.data)
+		assert.Equal(t, c.out, out, "tmpl: %s", c.tmpl)
+	}
+}

routers/web/repo/issue_view.go

@@ -284,7 +284,7 @@ func handleViewIssueRedirectExternal(ctx *context.Context) {
 			if extIssueUnit.ExternalTrackerConfig().ExternalTrackerStyle == markup.IssueNameStyleNumeric || extIssueUnit.ExternalTrackerConfig().ExternalTrackerStyle == "" {
 				metas := ctx.Repo.Repository.ComposeCommentMetas(ctx)
 				metas["index"] = ctx.PathParam("index")
-				res, err := vars.Expand(extIssueUnit.ExternalTrackerConfig().ExternalTrackerFormat, metas)
+				res, err := vars.ExpandCurlyBrace(extIssueUnit.ExternalTrackerConfig().ExternalTrackerFormat, metas)
 				if err != nil {
 					log.Error("unable to expand template vars for issue url. issue: %s, err: %v", metas["index"], err)
 					ctx.ServerError("Expand", err)

services/pull/merge.go

@@ -32,6 +32,7 @@ import (
 	"gitea.dev/modules/references"
 	repo_module "gitea.dev/modules/repository"
 	"gitea.dev/modules/setting"
+	"gitea.dev/modules/templates/vars"
 	"gitea.dev/modules/timeutil"
 	"gitea.dev/modules/util"
 	issue_service "gitea.dev/services/issue"
@@ -66,17 +67,15 @@ func getMergeMessage(ctx context.Context, baseGitRepo *git.Repository, pr *issue
 	reviewedBy := pr.GetApprovers(ctx)
 
 	if mergeStyle != "" {
-		templateFilepath := fmt.Sprintf(".gitea/default_merge_message/%s_TEMPLATE.md", strings.ToUpper(string(mergeStyle)))
 		commit, err := baseGitRepo.GetBranchCommit(ctx, pr.BaseRepo.DefaultBranch)
 		if err != nil {
 			return "", "", err
 		}
-		templateContent, err := commit.GetFileContent(ctx, baseGitRepo, templateFilepath, setting.Repository.PullRequest.DefaultMergeMessageSize)
+		templateContent, err := resolveMergeMessageTemplate(ctx, baseGitRepo, commit, mergeStyle)
 		if err != nil {
-			if !git.IsErrNotExist(err) {
-				return "", "", err
-			}
-		} else {
+			return "", "", err
+		}
+		if templateContent != "" {
 			vars := map[string]string{
 				"BaseRepoOwnerName":      pr.BaseRepo.OwnerName,
 				"BaseRepoName":           pr.BaseRepo.Name,
@@ -146,14 +145,32 @@ func getMergeMessage(ctx context.Context, baseGitRepo *git.Repository, pr *issue
 	return fmt.Sprintf("Merge pull request '%s' (%s%d) from %s:%s into %s", pr.Issue.Title, issueReference, pr.Issue.Index, pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseBranch), body, nil
 }
 
-func expandDefaultMergeMessage(template string, vars map[string]string) (message, body string) {
+// resolveMergeMessageTemplate returns the content of the merge message template for the given
+// merge style. It first looks for a style-specific template ({STYLE}_TEMPLATE.md), and falls back
+// to the generic DEFAULT_TEMPLATE.md if the style-specific one is not found.
+func resolveMergeMessageTemplate(ctx context.Context, baseGitRepo *git.Repository, commit *git.Commit, mergeStyle repo_model.MergeStyle) (string, error) {
+	templateFilepath := fmt.Sprintf(".gitea/default_merge_message/%s_TEMPLATE.md", strings.ToUpper(string(mergeStyle)))
+	templateContent, err := commit.GetFileContent(ctx, baseGitRepo, templateFilepath, setting.Repository.PullRequest.DefaultMergeMessageSize)
+	if err == nil {
+		return templateContent, nil
+	}
+	if !git.IsErrNotExist(err) {
+		return "", err
+	}
+	templateContent, err = commit.GetFileContent(ctx, baseGitRepo, ".gitea/default_merge_message/DEFAULT_TEMPLATE.md", setting.Repository.PullRequest.DefaultMergeMessageSize)
+	if err == nil || git.IsErrNotExist(err) {
+		return templateContent, nil
+	}
+	return "", err
+}
+
+func expandDefaultMergeMessage(template string, varsMap map[string]string) (message, body string) {
 	message = strings.TrimSpace(template)
 	if splits := strings.SplitN(message, "\n", 2); len(splits) == 2 {
 		message = splits[0]
 		body = strings.TrimSpace(splits[1])
 	}
-	mapping := func(s string) string { return vars[s] }
-	return os.Expand(message, mapping), os.Expand(body, mapping)
+	return vars.ExpandShellLike(message, varsMap), vars.ExpandShellLike(body, varsMap)
 }
 
 // GetDefaultMergeMessage returns default message used when merging pull request

services/pull/merge_test.go

@@ -4,9 +4,13 @@
 package pull
 
 import (
+	"path/filepath"
 	"testing"
 
+	"gitea.dev/modules/git"
+
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func Test_expandDefaultMergeMessage(t *testing.T) {
@@ -90,3 +94,47 @@ func TestAddCommitMessageTailer(t *testing.T) {
 	assert.Equal(t, "title\n\nTest-tailer: v1\nTest-tailer: v2", AddCommitMessageTailer("title\n\nTest-tailer: v1", "Test-tailer", "v2"))
 	assert.Equal(t, "title\n\nTest-tailer: v1\nTest-tailer: v2", AddCommitMessageTailer("title\n\nTest-tailer: v1\n", "Test-tailer", "v2"))
 }
+
+func TestResolveMergeMessageTemplate(t *testing.T) {
+	t.Run("NoDefault", func(t *testing.T) {
+		repo, err := git.ForceFastImportWithInit(t.Context(), filepath.Join(t.TempDir(), "test-repo"), []git.FastImportCommit{
+			{Ref: "refs/heads/master", Files: []git.FastImportFile{
+				{Path: ".gitea/default_merge_message/REBASE_TEMPLATE.md", Content: "rebase template"},
+			}},
+		})
+		require.NoError(t, err)
+		gitRepo, err := git.OpenRepository(t.Context(), repo)
+		require.NoError(t, err)
+		defer gitRepo.Close()
+
+		commit, err := gitRepo.GetBranchCommit(t.Context(), "master")
+		require.NoError(t, err)
+		tmpl, err := resolveMergeMessageTemplate(t.Context(), gitRepo, commit, "merge")
+		assert.NoError(t, err)
+		assert.Equal(t, "", tmpl)
+		tmpl, err = resolveMergeMessageTemplate(t.Context(), gitRepo, commit, "rebase")
+		assert.NoError(t, err)
+		assert.Equal(t, "rebase template", tmpl)
+	})
+	t.Run("WithDefault", func(t *testing.T) {
+		repo, err := git.ForceFastImportWithInit(t.Context(), filepath.Join(t.TempDir(), "test-repo"), []git.FastImportCommit{
+			{Ref: "refs/heads/master", Files: []git.FastImportFile{
+				{Path: ".gitea/default_merge_message/DEFAULT_TEMPLATE.md", Content: "default template"},
+				{Path: ".gitea/default_merge_message/REBASE_TEMPLATE.md", Content: "rebase template"},
+			}},
+		})
+		require.NoError(t, err)
+		gitRepo, err := git.OpenRepository(t.Context(), repo)
+		require.NoError(t, err)
+		defer gitRepo.Close()
+
+		commit, err := gitRepo.GetBranchCommit(t.Context(), "master")
+		require.NoError(t, err)
+		tmpl, err := resolveMergeMessageTemplate(t.Context(), gitRepo, commit, "merge")
+		assert.NoError(t, err)
+		assert.Equal(t, "default template", tmpl)
+		tmpl, err = resolveMergeMessageTemplate(t.Context(), gitRepo, commit, "rebase")
+		assert.NoError(t, err)
+		assert.Equal(t, "rebase template", tmpl)
+	})
+}

services/repository/create.go

@@ -91,7 +91,7 @@ func prepareRepoCommit(ctx context.Context, repo *repo_model.Repository, tmpDir
 		"CloneURL.HTTPS": cloneLink.HTTPS,
 		"OwnerName":      repo.OwnerName,
 	}
-	res, err := vars.Expand(string(data), match)
+	res, err := vars.ExpandCurlyBrace(string(data), match)
 	if err != nil {
 		// here we could just log the error and continue the rendering
 		log.Error("unable to expand template vars for repo README: %s, err: %v", opts.Readme, err)

services/repository/generate.go

@@ -24,6 +24,7 @@ import (
 	"gitea.dev/modules/log"
 	repo_module "gitea.dev/modules/repository"
 	"gitea.dev/modules/setting"
+	"gitea.dev/modules/templates/vars"
 	"gitea.dev/modules/util"
 
 	"github.com/huandu/xstrings"
@@ -86,12 +87,7 @@ func generateExpansion(ctx context.Context, src string, templateRepo, generateRe
 		}
 	}
 
-	return os.Expand(src, func(key string) string {
-		if val, ok := expansionMap[key]; ok {
-			return val
-		}
-		return key
-	})
+	return vars.ExpandShellLike(src, expansionMap)
 }
 
 type giteaTemplateFileMatcher struct {