Project refactor, add anthropic API support

- Split pkg/cli/cmd.go into new pkg/cmd package
- Split pkg/cli/functions.go into pkg/lmcli/tools package
- Refactor pkg/cli/openai.go to pkg/lmcli/provider/openai

Other changes:

- Made models configurable
- Slight config reorganization

pkg/cmd/retry.go

@@ -0,0 +1,58 @@
+package cmd
+
+import (
+	"fmt"
+
+	cmdutil "git.mlow.ca/mlow/lmcli/pkg/cmd/util"
+	"git.mlow.ca/mlow/lmcli/pkg/lmcli"
+	"git.mlow.ca/mlow/lmcli/pkg/lmcli/model"
+	"github.com/spf13/cobra"
+)
+
+func RetryCmd(ctx *lmcli.Context) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "retry <conversation>",
+		Short: "Retry the last user reply in a conversation",
+		Long:  `Re-prompt the conversation up to the last user response. Can be used to regenerate the last assistant reply, or simply generate one if an error occurred.`,
+		Args: func(cmd *cobra.Command, args []string) error {
+			argCount := 1
+			if err := cobra.MinimumNArgs(argCount)(cmd, args); err != nil {
+				return err
+			}
+			return nil
+		},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			shortName := args[0]
+			conversation := cmdutil.LookupConversation(ctx, shortName)
+
+			messages, err := ctx.Store.Messages(conversation)
+			if err != nil {
+				return fmt.Errorf("Could not retrieve messages for conversation: %s", conversation.Title)
+			}
+
+			// walk backwards through the conversation and delete messages, break
+			// when we find the latest user response
+			for i := len(messages) - 1; i >= 0; i-- {
+				if messages[i].Role == model.MessageRoleUser {
+					break
+				}
+
+				err = ctx.Store.DeleteMessage(&messages[i])
+				if err != nil {
+					lmcli.Warn("Could not delete previous reply: %v\n", err)
+				}
+			}
+
+			cmdutil.HandleConversationReply(ctx, conversation, true)
+			return nil
+		},
+		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+			compMode := cobra.ShellCompDirectiveNoFileComp
+			if len(args) != 0 {
+				return nil, compMode
+			}
+			return ctx.Store.ConversationShortNameCompletions(toComplete), compMode
+		},
+	}
+	return cmd
+}