Update command flag handling

`lmcli chat` now supports common prompt flags (model, length, system
prompt, etc)

pkg/lmcli/lmcli.go

@@ -10,17 +10,20 @@ import (
 	"git.mlow.ca/mlow/lmcli/pkg/lmcli/provider/anthropic"
 	"git.mlow.ca/mlow/lmcli/pkg/lmcli/provider/openai"
 	"git.mlow.ca/mlow/lmcli/pkg/lmcli/tools"
+	"git.mlow.ca/mlow/lmcli/pkg/util"
 	"git.mlow.ca/mlow/lmcli/pkg/util/tty"
 	"gorm.io/driver/sqlite"
 	"gorm.io/gorm"
 )
 
 type Context struct {
-	Config *Config
+	Config *Config // may be updated at runtime
 	Store  ConversationStore
 
 	Chroma       *tty.ChromaHighlighter
 	EnabledTools []model.Tool
+
+	SystemPromptFile string
 }
 
 func NewContext() (*Context, error) {
@@ -50,7 +53,7 @@ func NewContext() (*Context, error) {
 		}
 	}
 
-	return &Context{config, store, chroma, enabledTools}, nil
+	return &Context{config, store, chroma, enabledTools, ""}, nil
 }
 
 func (c *Context) GetModels() (models []string) {
@@ -96,6 +99,17 @@ func (c *Context) GetCompletionProvider(model string) (provider.ChatCompletionCl
 	return nil, fmt.Errorf("unknown model: %s", model)
 }
 
+func (c *Context) GetSystemPrompt() string {
+	if c.SystemPromptFile != "" {
+		content, err := util.ReadFileContents(c.SystemPromptFile)
+		if err != nil {
+			Fatal("Could not read file contents at %s: %v\n", c.SystemPromptFile, err)
+		}
+		return content
+	}
+	return *c.Config.Defaults.SystemPrompt
+}
+
 func configDir() string {
 	var configDir string