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/tree.go

@@ -7,6 +7,7 @@ package git
 import (
 	"bytes"
 	"context"
+	"io"
 	"strings"
 
 	"gitea.dev/modules/git/gitcmd"
@@ -76,3 +77,97 @@ func (repo *Repository) GetTreePathLatestCommit(ctx context.Context, refName, tr
 	}
 	return repo.GetCommit(ctx, strings.TrimSpace(stdout))
 }
+
+// Tree represents a flat directory listing.
+type Tree struct {
+	TreeCommon
+
+	entries       Entries
+	entriesParsed bool
+}
+
+// ListEntries returns all entries of current tree.
+func (t *Tree) ListEntries(ctx context.Context, gitRepo *Repository) (Entries, error) {
+	if t.entriesParsed {
+		return t.entries, nil
+	}
+
+	batch, cancel, err := gitRepo.CatFileBatch()
+	if err != nil {
+		return nil, err
+	}
+	defer cancel()
+
+	info, rd, err := batch.QueryContent(t.ID.String())
+	if err != nil {
+		return nil, err
+	}
+
+	if info.Type == "commit" {
+		treeID, err := ReadTreeID(rd, info.Size)
+		if err != nil && err != io.EOF {
+			return nil, err
+		}
+		info, rd, err = batch.QueryContent(treeID)
+		if err != nil {
+			return nil, err
+		}
+	}
+	if info.Type == "tree" {
+		t.entries, err = catBatchParseTreeEntries(t.ID.Type(), t, rd, info.Size)
+		if err != nil {
+			return nil, err
+		}
+		t.entriesParsed = true
+		return t.entries, nil
+	}
+
+	// Not a tree just use ls-tree instead
+	if err := DiscardFull(rd, info.Size+1); err != nil {
+		return nil, err
+	}
+
+	stdout, _, runErr := gitcmd.NewCommand("ls-tree", "-l").AddDynamicArguments(t.ID.String()).WithRepo(gitRepo).RunStdBytes(ctx)
+	if runErr != nil {
+		if gitcmd.IsStderr(runErr, gitcmd.StderrNotValidObjectName) || gitcmd.IsStderr(runErr, gitcmd.StderrNotTreeObject) {
+			return nil, ErrNotExist{
+				ID: t.ID.String(),
+			}
+		}
+		return nil, runErr
+	}
+
+	t.entries, err = parseTreeEntries(stdout, t)
+	if err == nil {
+		t.entriesParsed = true
+	}
+
+	return t.entries, err
+}
+
+// listEntriesRecursive returns all entries of current tree recursively including all subtrees
+// extraArgs could be "-l" to get the size, which is slower
+func (t *Tree) listEntriesRecursive(ctx context.Context, gitRepo *Repository, extraArgs gitcmd.TrustedCmdArgs) (Entries, error) {
+	stdout, _, runErr := gitcmd.NewCommand("ls-tree", "-t", "-r").
+		AddArguments(extraArgs...).
+		AddDynamicArguments(t.ID.String()).
+		WithRepo(gitRepo).
+		RunStdBytes(ctx)
+	if runErr != nil {
+		return nil, runErr
+	}
+
+	// FIXME: the "name" field is abused, here it is a full path
+	// FIXME: this ptree is not right, fortunately it isn't really used
+	return parseTreeEntries(stdout, t)
+}
+
+// ListEntriesRecursiveFast returns all entries of current tree recursively including all subtrees, no size
+func (t *Tree) ListEntriesRecursiveFast(ctx context.Context, gitRepo *Repository) (Entries, error) {
+	return t.listEntriesRecursive(ctx, gitRepo, nil)
+}
+
+// ListEntriesRecursiveWithSize returns all entries of current tree recursively including all subtrees, with size
+func (t *Tree) ListEntriesRecursiveWithSize(ctx context.Context, gitRepo *Repository) (Entries, error) {
+	return t.listEntriesRecursive(ctx, gitRepo, gitcmd.TrustedCmdArgs{"--long"})
+}