refactor!: remove go-git backend (#39487)

Removes the go-git backend so every build uses the git CLI backend. Its
Windows performance advantage is gone, it lacks SHA-256 support, and it
breaks repositories on Windows.

The performance changes moved to
https://github.com/go-gitea/gitea/pull/39526.

Fixes https://github.com/go-gitea/gitea/issues/38359
Fixes https://github.com/go-gitea/gitea/issues/34694

---------

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

modules/git/repo_ref.go

@@ -4,7 +4,9 @@
 package git
 
 import (
+	"bufio"
 	"context"
+	"io"
 	"strings"
 
 	"gitea.dev/modules/git/gitcmd"
@@ -96,3 +98,64 @@ func (repo *Repository) UnstableGuessRefByShortName(ctx context.Context, shortNa
 	}
 	return ""
 }
+
+// GetRefsFiltered returns all references of the repository that matches patterm exactly or starting with.
+func (repo *Repository) GetRefsFiltered(ctx context.Context, pattern string) ([]*Reference, error) {
+	refs := make([]*Reference, 0)
+	cmd := gitcmd.NewCommand("for-each-ref")
+	stdoutReader, stdoutReaderClose := cmd.MakeStdoutPipe()
+	defer stdoutReaderClose()
+	err := cmd.WithRepo(repo).
+		WithPipelineFunc(func(context gitcmd.Context) error {
+			bufReader := bufio.NewReader(stdoutReader)
+			for {
+				// The output of for-each-ref is simply a list:
+				// <sha> SP <type> TAB <ref> LF
+				sha, err := bufReader.ReadString(' ')
+				if err == io.EOF {
+					break
+				}
+				if err != nil {
+					return err
+				}
+				sha = sha[:len(sha)-1]
+
+				typ, err := bufReader.ReadString('\t')
+				if err == io.EOF {
+					// This should not happen, but we'll tolerate it
+					break
+				}
+				if err != nil {
+					return err
+				}
+				typ = typ[:len(typ)-1]
+
+				refName, err := bufReader.ReadString('\n')
+				if err == io.EOF {
+					// This should not happen, but we'll tolerate it
+					break
+				}
+				if err != nil {
+					return err
+				}
+				refName = refName[:len(refName)-1]
+
+				// refName cannot be HEAD but can be remotes or stash
+				if strings.HasPrefix(refName, RemotePrefix) || refName == "/refs/stash" {
+					continue
+				}
+
+				if pattern == "" || strings.HasPrefix(refName, pattern) {
+					r := &Reference{
+						Name:   refName,
+						Object: MustIDFromString(sha),
+						Type:   typ,
+						repo:   repo,
+					}
+					refs = append(refs, r)
+				}
+			}
+			return nil
+		}).RunWithStderr(ctx)
+	return refs, err
+}