[CHORE] Drop go-git support

See https://codeberg.org/forgejo/discussions/issues/164 for the
rationale and discussion of this change.

Everything related to the `go-git` dependency is dropped (Only a single
instance is left in a test file to test for an XSS, it requires crafting
an commit that Git itself refuses to craft). `_gogit` files have
been removed entirely, `go:build: !gogit` is removed, `XXX_nogogit.go` files
either have been renamed or had their code being merged into the
`XXX.go` file.

modules/git/tree.go

@@ -6,9 +6,26 @@ package git
 
 import (
 	"bytes"
+	"io"
 	"strings"
 )
 
+// Tree represents a flat directory listing.
+type Tree struct {
+	ID         ObjectID
+	ResolvedID ObjectID
+	repo       *Repository
+
+	// parent tree
+	ptree *Tree
+
+	entries       Entries
+	entriesParsed bool
+
+	entriesRecursive       Entries
+	entriesRecursiveParsed bool
+}
+
 // NewTree create a new tree according the repository and tree id
 func NewTree(repo *Repository, id ObjectID) *Tree {
 	return &Tree{
@@ -17,6 +34,100 @@ func NewTree(repo *Repository, id ObjectID) *Tree {
 	}
 }
 
+// ListEntries returns all entries of current tree.
+func (t *Tree) ListEntries() (Entries, error) {
+	if t.entriesParsed {
+		return t.entries, nil
+	}
+
+	if t.repo != nil {
+		wr, rd, cancel := t.repo.CatFileBatch(t.repo.Ctx)
+		defer cancel()
+
+		_, _ = wr.Write([]byte(t.ID.String() + "\n"))
+		_, typ, sz, err := ReadBatchLine(rd)
+		if err != nil {
+			return nil, err
+		}
+		if typ == "commit" {
+			treeID, err := ReadTreeID(rd, sz)
+			if err != nil && err != io.EOF {
+				return nil, err
+			}
+			_, _ = wr.Write([]byte(treeID + "\n"))
+			_, typ, sz, err = ReadBatchLine(rd)
+			if err != nil {
+				return nil, err
+			}
+		}
+		if typ == "tree" {
+			t.entries, err = catBatchParseTreeEntries(t.ID.Type(), t, rd, sz)
+			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, sz+1); err != nil {
+			return nil, err
+		}
+	}
+
+	stdout, _, runErr := NewCommand(t.repo.Ctx, "ls-tree", "-l").AddDynamicArguments(t.ID.String()).RunStdBytes(&RunOpts{Dir: t.repo.Path})
+	if runErr != nil {
+		if strings.Contains(runErr.Error(), "fatal: Not a valid object name") || strings.Contains(runErr.Error(), "fatal: not a tree object") {
+			return nil, ErrNotExist{
+				ID: t.ID.String(),
+			}
+		}
+		return nil, runErr
+	}
+
+	var err error
+	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(extraArgs TrustedCmdArgs) (Entries, error) {
+	if t.entriesRecursiveParsed {
+		return t.entriesRecursive, nil
+	}
+
+	stdout, _, runErr := NewCommand(t.repo.Ctx, "ls-tree", "-t", "-r").
+		AddArguments(extraArgs...).
+		AddDynamicArguments(t.ID.String()).
+		RunStdBytes(&RunOpts{Dir: t.repo.Path})
+	if runErr != nil {
+		return nil, runErr
+	}
+
+	var err error
+	t.entriesRecursive, err = parseTreeEntries(stdout, t)
+	if err == nil {
+		t.entriesRecursiveParsed = true
+	}
+
+	return t.entriesRecursive, err
+}
+
+// ListEntriesRecursiveFast returns all entries of current tree recursively including all subtrees, no size
+func (t *Tree) ListEntriesRecursiveFast() (Entries, error) {
+	return t.listEntriesRecursive(nil)
+}
+
+// ListEntriesRecursiveWithSize returns all entries of current tree recursively including all subtrees, with size
+func (t *Tree) ListEntriesRecursiveWithSize() (Entries, error) {
+	return t.listEntriesRecursive(TrustedCmdArgs{"--long"})
+}
+
 // SubTree get a sub tree by the sub dir path
 func (t *Tree) SubTree(rpath string) (*Tree, error) {
 	if len(rpath) == 0 {