knotserver: set default git committer user via config

Introducing `KNOT_GIT_USER_NAME` and `KNOT_GIT_USER_EMAIL` environment
variables.

This will prevent silently inheritting global gitconfig's user

Signed-off-by: Seongmin Lee <[e-mail]>

knotserver/config/config.go

···
 	Dev bool `env:"DEV, default=false"`
 }
 
+type Git struct {
+	// user name & email used as committer
+	UserName     string `env:"USER_NAME, default=Tangled"`
+	UserEmail    string `env:"USER_EMAIL, default=[e-mail]"`
+}
+
 func (s Server) Did() syntax.DID {
 	return syntax.DID(fmt.Sprintf("did:web:%s", s.Hostname))
 }
···
 type Config struct {
 	Repo            Repo   `env:",prefix=KNOT_REPO_"`
 	Server          Server `env:",prefix=KNOT_SERVER_"`
+	Git             Git    `env:",prefix=KNOT_GIT_"`
 	AppViewEndpoint string `env:"APPVIEW_ENDPOINT, default=https://tangled.sh"`
 }
 

knotserver/git/merge.go

···
 
 // MergeOptions specifies the configuration for a merge operation
 type MergeOptions struct {
-	CommitMessage string
-	CommitBody    string
-	AuthorName    string
-	AuthorEmail   string
-	FormatPatch   bool
+	CommitMessage  string
+	CommitBody     string
+	AuthorName     string
+	AuthorEmail    string
+	CommitterName  string
+	CommitterEmail string
+	FormatPatch    bool
 }
 
 func (e ErrMerge) Error() string {
···
 	var stderr bytes.Buffer
 	var cmd *exec.Cmd
 
+	// configure default git user before merge
+	exec.Command("git", "-C", tmpDir, "config", "user.name", opts.CommitterName).Run()
+	exec.Command("git", "-C", tmpDir, "config", "user.email", opts.CommitterEmail).Run()
 	exec.Command("git", "-C", tmpDir, "config", "advice.mergeConflict", "false").Run()
 
 	// if patch is a format-patch, apply using 'git am'
···
 		authorName := opts.AuthorName
 		authorEmail := opts.AuthorEmail
 
-		if authorEmail == "" {
-			authorEmail = "[e-mail]"
-		}
-
-		if authorName == "" {
-			authorName = "Tangled"
-		}
-
-		if authorName != "" {
+		if authorName != "" && authorEmail != "" {
 			commitArgs = append(commitArgs, "--author", fmt.Sprintf("%s <%s>", authorName, authorEmail))
 		}
+		// else, will default to knot's global user.name & user.email configured via `KNOT_GIT_USER_*` env variables
 
 		commitArgs = append(commitArgs, "-m", opts.CommitMessage)
 

knotserver/xrpc/merge.go

···
 		mo.CommitMessage = *data.CommitMessage
 	}
 
+	mo.CommitterName =  x.Config.Git.UserName
+	mo.CommitterEmail = x.Config.Git.UserEmail
 	mo.FormatPatch = patchutil.IsFormatPatch(data.Patch)
 
 	err = gr.MergeWithOptions([]byte(data.Patch), data.Branch, mo)