Add terminal color choosing support

[ulyssessouza]

This adds the capability of choosing the color to print in the terminal by just setting an envvar called BUILDKIT_TERM_COLOR.

Note that this is a "follow-up" of #2368 making it more flexible so that the users can choose it's preferred color depending on their terminal themes and preferences.

It supports the following values:

"default"

"black"
"red"
"green"
"yellow"
"blue"
"magenta"
"cyan"
"white"

"light-black"
"light-red"
"light-green"
"light-yellow"
"light-blue"
"light-magenta"
"light-cyan"
"light-white"

[tonistiigi]

Is there a convention for this? I know NO_COLOR is a thing but this looks somewhat weird as there isn't just one color. You are changing the color of the completed item but iirc we have 4 possible different colors used by this progressbar.

[ulyssessouza]

AFAIC there is not convention on terminal color naming. I just took the ones from "github.com/morikuni/aec" in lower case.

This PR only affects the "typical buildkit blue" color and not the other 3. It's not a complete theme (I actually like the idea of having it 😺).

[tonistiigi]

@crazy-max wdyt?

I think we could definitely support NO_COLOR and if there is a known convention for passing additional colors via env it would probably be ok. Only one I know about is LS_COLORS but that uses a different format. Do we want to define a similar key=index: format for this? https://geoff.greer.fm/lscolors/ . All this could also be in aec level though.

Currently just having a special env for overriding one specific color seems too hacky to me.

[crazy-max]

Yes agree that we should support NO_COLOR, probably upstream on https://github.com/morikuni/aec like go-ansi has done.

I'm not aware of a convention but we should also support cancel and error states (probably also warning #2498 in the future). Maybe with a key like you said @tonistiigi BUILDKIT_TERM_COLOR=run=blue,cancel=yellow,error=red?

[crazy-max]

As discussed using LS_COLORS lgtm. e.g., LS_COLORS=ru=blue:ca=yellow:er=red:wa=orange

• ru: run output
• ca: cancel output
• er: error output
• wa: warning output (in a follow-up for this one, see Updates to warnings handling #2498)

[tonistiigi]

So not LS_COLORS directly but similar logic. BUILDKIT_COLORS. Or maybe could be AEC_COLORS=31=34: as well.

Keys do not need to be 2 chars and there is no "orange".

[spkane]

@ulyssessouza Is this PR being actively worked on still, based on the feedback? I would love to see this functionality implemented in buildkit.

[ulyssessouza]

@spkane I'll finish that soon... Just trying to make a bit of time here... Wouldn't take much time

[spkane]

@ulyssessouza I took a stab at this in another PR (#2954), because I had some time and the desire to try and implement this. I'd appreciate hearing what you think.

[crazy-max]

fixed by #2954