--watch mode interacts poorly when stdout is not a TTY

[kevinburke1]

I use a process manager to start both esbuild in --watch mode and nginx (which we use to terminate TLS for local development)

watch:
	goreman --set-ports=false --exit-on-error start

This reads the instructions out of a Procfile

alb: nginx -p ./fs -c etc/nginx/nginx.conf
watcher: ./node_modules/.bin/esbuild --watch --color=false src/index.jsx

Each time the three dots change, a new line is drawn to the output:

$ make watch
envdir envs/localdev goreman --set-ports=false --exit-on-error start
15:23:38     alb | nginx: [alert] could not open error log file: open() "/usr/local/var/log/nginx/error.log" failed (13: Permission denied)
15:23:38 watcher | ~/src/github.com/meterup/dashboard ~/src/github.com/meterup/dashboard
15:23:38 watcher | + ./node_modules/.bin/esbuild ./src/index.jsx --watch --color=false
▫▫▫ 3:39 watcher |
▪▫▫ 3:39 watcher |
▪▪▫ 3:40 watcher |
▪▪▪ 3:40 watcher |
▫▪▪ 3:41 watcher |
▫▫▪ 3:41 watcher |

It would be nice if the --watch tool could detect a TTY and avoid printing the bubbles if so, since they just clutter the screen.

Further, echoing the request in #751 it would be nice if it was possible to see somehow that esbuild was detecting changes and doing something, especially since the rebuild process is polling-driven and not file-event driven.

[evanw]

See also #742. You can use the log level option to disable this in the meantime.