feat(repo): prioritize well-known READMEs and optimize discovery (#38532)

This PR adjusts the repository README discovery logic to mirror GitHub's
priority order, while retaining support for Gitea's specific `.gitea/`
directory.

Previously, Gitea would prioritize a `README.md` at the root of the
repository over any READMEs in `.gitea/` or `.github/`. With this
change, well-known subdirectories are evaluated first when viewing the
repository root.

**New Priority Order:**
1. `.gitea/README.md`
2. `.github/README.md`
3. `/README.md` (root directory)
4. `docs/README.md`

This allows repository maintainers to use `.github/README.md` (or
`.gitea/README.md`) as the repository homepage without having to remove
or rename generic root `/README.md` files required by package managers
(like NPM, Crates.io, Docker, etc.).

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/git/fastimport.go

@@ -0,0 +1,42 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+
+	"gitea.dev/modules/git/gitcmd"
+)
+
+type FastImportFile struct {
+	Mode    EntryMode
+	Path    string
+	Content string
+}
+
+type FastImportCommit struct {
+	Ref     string
+	Message string
+	Files   []FastImportFile
+}
+
+// ForceFastImport is for mainly for testing purpose
+func ForceFastImport(ctx context.Context, repo RepositoryFacade, commits []FastImportCommit) error {
+	var buf bytes.Buffer
+	for i, c := range commits {
+		_, _ = fmt.Fprintf(&buf, "reset %s\n", c.Ref)
+		_, _ = fmt.Fprintf(&buf, "commit %s\nmark :%d\ncommitter Gitea <gitea@example.com> 1500000000 +0000\n", c.Ref, i+1)
+		_, _ = fmt.Fprintf(&buf, "data %d\n%s\n", len(c.Message), c.Message)
+		for _, f := range c.Files {
+			_, _ = fmt.Fprintf(&buf, "M %s inline %s\ndata %d\n%s\n", f.Mode.String(), f.Path, len(f.Content), f.Content)
+		}
+	}
+	buf.WriteString("done\n")
+	_, _, err := gitcmd.NewCommand("fast-import").AddArguments("--force", "--done").
+		WithRepo(repo).WithStdinBytes(buf.Bytes()).
+		RunStdString(ctx)
+	return err
+}