Migrate temp_repo.go to use git.NewCommand (#8918)

This PR migrates temp_repo.go to use git.NewCommand instead creating processes by itself - this fixes the problem underlying PR #8905.

There are other places that run git outside of the controlled locale defined in #8548 but temp_repo.go is the only cause of failure of local testing in cases where English is not the default - implying that error messages from those other commands are not interpreted.

Replaces #8905

modules/git/command.go

@@ -67,6 +67,13 @@ func (c *Command) RunInDirTimeoutEnvPipeline(env []string, timeout time.Duration
 // RunInDirTimeoutEnvFullPipeline executes the command in given directory with given timeout,
 // it pipes stdout and stderr to given io.Writer and passes in an io.Reader as stdin.
 func (c *Command) RunInDirTimeoutEnvFullPipeline(env []string, timeout time.Duration, dir string, stdout, stderr io.Writer, stdin io.Reader) error {
+	return c.RunInDirTimeoutEnvFullPipelineFunc(env, timeout, dir, stdout, stderr, stdin, nil)
+}
+
+// RunInDirTimeoutEnvFullPipelineFunc executes the command in given directory with given timeout,
+// it pipes stdout and stderr to given io.Writer and passes in an io.Reader as stdin. Between cmd.Start and cmd.Wait the passed in function is run.
+func (c *Command) RunInDirTimeoutEnvFullPipelineFunc(env []string, timeout time.Duration, dir string, stdout, stderr io.Writer, stdin io.Reader, fn func(context.Context, context.CancelFunc)) error {
+
 	if timeout == -1 {
 		timeout = DefaultCommandExecutionTimeout
 	}
@@ -98,6 +105,10 @@ func (c *Command) RunInDirTimeoutEnvFullPipeline(env []string, timeout time.Dura
 	pid := process.GetManager().Add(fmt.Sprintf("%s %s %s [repo_path: %s]", GitExecutable, c.name, strings.Join(c.args, " "), dir), cmd)
 	defer process.GetManager().Remove(pid)
 
+	if fn != nil {
+		fn(ctx, cancel)
+	}
+
 	if err := cmd.Wait(); err != nil {
 		return err
 	}