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.

modules/repository/init.go

@@ -316,9 +316,8 @@ func initRepoCommit(ctx context.Context, tmpPath string, repo *repo_model.Reposi
 		return fmt.Errorf("git add --all: %w", err)
 	}
 
-	cmd := git.NewCommand(ctx, "commit").
-		AddOptionFormat("--author='%s <%s>'", sig.Name, sig.Email).
-		AddOptionValues("-m", "Initial commit")
+	cmd := git.NewCommand(ctx, "commit", "--message=Initial commit").
+		AddOptionFormat("--author='%s <%s>'", sig.Name, sig.Email)
 
 	sign, keyID, signer, _ := asymkey_service.SignInitialCommit(ctx, tmpPath, u)
 	if sign {

services/pull/merge.go

@@ -533,7 +533,7 @@ func rawMerge(ctx context.Context, pr *issues_model.PullRequest, doer *user_mode
 		if err := git.NewCommand(ctx, "commit").
 			AddArguments(signArgs...).
 			AddOptionFormat("--author='%s <%s>'", sig.Name, sig.Email).
-			AddOptionValues("-m", message).
+			AddOptionFormat("--message=%s", message).
 			Run(&git.RunOpts{
 				Env:    env,
 				Dir:    tmpBasePath,
@@ -641,7 +641,7 @@ func rawMerge(ctx context.Context, pr *issues_model.PullRequest, doer *user_mode
 
 func commitAndSignNoAuthor(ctx context.Context, pr *issues_model.PullRequest, message string, signArgs git.TrustedCmdArgs, tmpBasePath string, env []string) error {
 	var outbuf, errbuf strings.Builder
-	if err := git.NewCommand(ctx, "commit").AddArguments(signArgs...).AddOptionValues("-m", message).
+	if err := git.NewCommand(ctx, "commit").AddArguments(signArgs...).AddOptionFormat("--message=%s", message).
 		Run(&git.RunOpts{
 			Env:    env,
 			Dir:    tmpBasePath,