fall back to simple text output when stdout is not a tty

[knQzx]

summary

• detect when stdout is not a tty and fall back to simple line-by-line status output
• fixes silent commands when piping to a file

fixes #113

test plan

before (main):

$ container image pull ghcr.io/linuxcontainers/alpine:3.20 2>stderr.txt
$ cat stderr.txt
(empty - progress lost when stderr is not a tty)

after:

$ container image pull ghcr.io/linuxcontainers/alpine:3.20 2>stderr.txt
$ cat stderr.txt
[1/2] Fetching image [0s]
[1/2] Fetching image (7 of 15 blobs) [2s]
[1/2] Fetching image 42% (23 of 50 blobs, 10.0/23.7 MB, 6.9 MB/s) [5s]
[2/2] Unpacking image for platform linux/arm64 [11s]
...

also added TestCLIProgressAuto integration test covering auto/plain/none modes

[jglogan]

@knQzx Thank you for the PR! Could you please add the commands you tested with, and before/after output, to the PR description?

Would it be possible to add an integration test for this?

[knQzx]

added before/after output to the description and an integration test for this

[jglogan]

@knQzx It was a long time ago, but I think we made an implementation decision during initial progress bar development that if stderr wasn't a tty, we would suppress progress output, so that you'd only see warnings and errors.

I can think of an idea or two, but why is this change to include progress with the warnings and errors useful for you?

[knQzx]

@jglogan mainly for ci logs - when a pull runs in a pipeline and stderr goes to a file, it's hard to tell if things are progressing or stuck. what were the ideas you had in mind?