refactor: make git package handle all git operations (#38543)

before: gitrepo vs git packages
after: git package fully handle all git operations

by the way, use `WithRepo(repo)` instead of `WithDir(repo.Path)` to hide
path details.

benefits:

1. remove all unnecessary wrappers, developers no need to struggle with
"which package should be used"
2. simplify code, RepositoryFacade can (will) be used everywhere, all
"path" details are (will be) hidden

modules/git/commit_file.go

@@ -0,0 +1,88 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"bufio"
+	"context"
+	"io"
+
+	"gitea.dev/modules/git/gitcmd"
+	"gitea.dev/modules/log"
+)
+
+// CommitFileStatus represents status of files in a commit.
+type CommitFileStatus struct {
+	Added    []string
+	Removed  []string
+	Modified []string
+}
+
+// NewCommitFileStatus creates a CommitFileStatus
+func NewCommitFileStatus() *CommitFileStatus {
+	return &CommitFileStatus{
+		[]string{}, []string{}, []string{},
+	}
+}
+
+func parseCommitFileStatus(fileStatus *CommitFileStatus, stdout io.Reader) {
+	rd := bufio.NewReader(stdout)
+	peek, err := rd.Peek(1)
+	if err != nil {
+		if err != io.EOF {
+			log.Error("Unexpected error whilst reading from git log --name-status. Error: %v", err)
+		}
+		return
+	}
+	if peek[0] == '\n' || peek[0] == '\x00' {
+		_, _ = rd.Discard(1)
+	}
+	for {
+		modifier, err := rd.ReadString('\x00')
+		if err != nil {
+			if err != io.EOF {
+				log.Error("Unexpected error whilst reading from git log --name-status. Error: %v", err)
+			}
+			return
+		}
+		file, err := rd.ReadString('\x00')
+		if err != nil {
+			if err != io.EOF {
+				log.Error("Unexpected error whilst reading from git log --name-status. Error: %v", err)
+			}
+			return
+		}
+		file = file[:len(file)-1]
+		switch modifier[0] {
+		case 'A':
+			fileStatus.Added = append(fileStatus.Added, file)
+		case 'D':
+			fileStatus.Removed = append(fileStatus.Removed, file)
+		case 'M':
+			fileStatus.Modified = append(fileStatus.Modified, file)
+		}
+	}
+}
+
+// GetCommitFileStatus returns file status of commit in given repository.
+func GetCommitFileStatus(ctx context.Context, repo RepositoryFacade, commitID string) (*CommitFileStatus, error) {
+	cmd := gitcmd.NewCommand("log", "--name-status", "-m", "--pretty=format:", "--first-parent", "--no-renames", "-z", "-1")
+	stdout, stdoutClose := cmd.MakeStdoutPipe()
+	defer stdoutClose()
+	done := make(chan struct{})
+	fileStatus := NewCommitFileStatus()
+	go func() {
+		parseCommitFileStatus(fileStatus, stdout)
+		close(done)
+	}()
+	err := cmd.AddDynamicArguments(commitID).
+		WithRepo(repo).
+		RunWithStderr(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	<-done
+	return fileStatus, nil
+}