Use --message=%s for git commit message (#23028)

Close  #23027

`git commit` message option _only_ supports 4 formats (well, only ....):
* `"commit", "-m", msg`
* `"commit", "-m{msg}"`  (no space)
* `"commit", "--message", msg`
* `"commit", "--message={msg}"`

The long format with `=` is the best choice, and it's documented in `man
git-commit`:

`-m <msg>, --message=<msg> ...`

ps: I would suggest always use long format option for git command, as
much as possible.

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/git/commit.go

@@ -131,7 +131,7 @@ func CommitChangesWithArgs(repoPath string, args TrustedCmdArgs, opts CommitChan
 	if opts.Author != nil {
 		cmd.AddOptionFormat("--author='%s <%s>'", opts.Author.Name, opts.Author.Email)
 	}
-	cmd.AddOptionValues("-m", opts.Message)
+	cmd.AddOptionFormat("--message=%s", opts.Message)
 
 	_, _, err := cmd.RunStdString(&RunOpts{Dir: repoPath})
 	// No stderr but exit status 1 means nothing to commit.