[23.0 backport] docker ps: always use --quiet, also combined with --format

[thaJeztah]

• backport of docker ps: always use --quiet, also combined with --format #3666

---

• follow-up to Fix psFormat's Size handling in config file #3640
• see the discussion on cli/command: ps: only check format-template once photra/cli#1 (comment)
• fixes docker ps -q does not work if the config file contains a psFormat  #4093
• supersedes / closes cli: do not apply configfile's psFormat when --quiet is passed #4040

Previously, the formatter would ignore the quiet option if a custom format
was passed; this situation was handled in runPs(), where custom formats
would only be applied if the quiet option was not set, but only if the
format was set in the CLI's config.

This patch updates NewContainerFormat() to do the same, even if a --format
was passed on the command-line.

This is a change in behavior, so may need some discussion; possible alternatives;

• produce an error if both --format and --quiet are passed
• print a warning if both are passed (but use the logic from this patch)

Before this patch:

docker ps --format '{{.Image}}'
ubuntu:22.04
alpine

docker ps --format '{{.Image}}' --quiet
ubuntu:22.04
alpine

mkdir -p ~/.docker/
echo '{"psFormat": "{{.Image}}" > ~/.docker/config.json

docker ps
ubuntu:22.04
alpine

docker ps --quiet
ubuntu:22.04
alpine

With this patch applied:

docker ps --format '{{.Image}}'
ubuntu:22.04
alpine

docker ps --format '{{.Image}}' --quiet
40111f61d5c5
482efdf39fac

mkdir -p ~/.docker/
echo '{"psFormat": "{{.Image}}" > ~/.docker/config.json

docker ps
ubuntu:22.04
alpine

docker ps --quiet
40111f61d5c5
482efdf39fac

docker ps: print warning if both --format and --quiet are set

Of both "--quiet" and "--format" are set, --quiet takes precedence. This
patch adds a warning to inform the user that their custom format is not
used:

docker ps --format='{{.Image}}'
ubuntu:22.04
alpine

docker ps --format='{{.Image}}' --quiet
WARNING: Ignoring custom format, because both --format and --quiet are set.
40111f61d5c5
482efdf39fac

The warning is printed on STDERR, so can be redirected:

docker ps --format='{{.Image}}' --quiet 2> /dev/null
40111f61d5c5
482efdf39fac

The warning is only shown if the format is set using the "--format" option.
No warning is shown if a custom format is set through the CLI configuration
file:

mkdir -p ~/.docker/
echo '{"psFormat": "{{.Image}}"}' > ~/.docker/config.json

docker ps
ubuntu:22.04
alpine

docker ps --quiet
40111f61d5c5
482efdf39fac

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.84%. Comparing base (0b3f540) to head (de7e265).
Report is 177 commits behind head on 23.0.

Additional details and impacted files

@@           Coverage Diff           @@
##             23.0    #4201   +/-   ##
=======================================
  Coverage   58.83%   58.84%           
=======================================
  Files         572      572           
  Lines       49610    49620   +10     
=======================================
+ Hits        29188    29198   +10     
  Misses      18648    18648           
  Partials     1774     1774           

[thaJeztah]

Discussing with @neersighted whether or not to backport this to v23.0;

👍 fixes docker ps --quiet with a custom format in ~/.docker/config.json
👎 it's a change in behaviour (notably for docker ps --format {''some format"}} --quiet)

/cc @tianon @vvoland @cpuguy83 @AkihiroSuda WDYT?

[tianon]

No strong feelings - I don't think it needs a backport, but I think the new behavior is much more correct (and matches the user expectation better), so it's totally reasonable to backport if 23.x is going to continue to live for a while.

[thaJeztah]

FWIW; I discussed with @neersighted and he was okay with this change, but wanted to have a quick peek from others

[AkihiroSuda]

For v23, it might be safer to just retain the old behavior but print a warning message

[thaJeztah]

Yeah, I guess the "complicated" one is the case where both as passed through --flags. The case where a default is configured in the ~/.docker/config.json (and --quiet not working) is easier.

I could consider adding a commit that only changes the behaviour for ~/.docker/config.json for 23.0, and we can decide on the other ones later (or keep it)