cli/command/container: remove reportError, and put StatusError to use

[thaJeztah]

• follow-up to cmd/docker: split handling exit-code to a separate utility #5229
• follow-up to cli: make cli.StatusError slightly prettier #5231

The reportError utility was present because cli.StatusError would print the error decorated with Status: <error-message>, Code: <exit-code>. That was not desirable in many cases as it would mess-up the output. To prevent this, the CLI had code to check for an empty Status (error message) in which case the error would be "ignored" (and only used for the exit-status), and the reportError utility would be used to manually print a custom error message before returning the error.

Now that bca2090 fixed the output format of cli.StatusError, and 3dd6fc3 and 350a0b6 no longer discard these error, we can get rid of this utility, and just set the error-message for the status-error.

This patch:

• Introduces a withHelp which takes care of decorating errors with a "Run --help" hint for the user.
• Introduces a toStatusError utility that detects certain errors in the container to assign a corresponding exit-code (these error-codes can be used to distinguish "client" errors from "container" errors).
• Removes the reportError utility, and removes code that manually printed errors before returning.

Behavior is mostly unmodified, with the exception of some slight reformatting of the errors:

• withHelp adds a docker: prefix to the error, to indicate the error is produced by the docker command. This prefix was already present in most cases.
• The "--help" hint is slightly updated ("Run 'docker run --help' for more information" instead of "See 'docker run --help'"), to make it more clear that it's a "call to action".
• An empty is added before the "--help" hint to separate it better from the error-message.

Before this patch:

$ docker run --pull=invalid-option alpine
docker: invalid pull option: 'invalid-option': must be one of "always", "missing" or "never".
See 'docker run --help'.
$ echo $?
125

$ docker run --rm alpine nosuchcommand
docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "nosuchcommand": executable file not found in $PATH: unknown.
$ echo $?
127

With this patch:

$ docker run --pull=invalid-option alpine
docker: invalid pull option: 'invalid-option': must be one of "always", "missing" or "never"

Run 'docker run --help' for more information
$ echo $?
125

$ docker run --rm alpine nosuchcommand
docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "nosuchcommand": executable file not found in $PATH: unknown.

Run 'docker run --help' for more information
$ echo $?
127

[thaJeztah]

Slight change here; previously we would print the error before the container was removed; this would be for the "old API, --rm running on the client-side" case. I don't think this would make much of a difference in practice, and it would only be for old API versions (API 1.24 I think?)

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 40.00000% with 21 lines in your changes missing coverage. Please review.

Project coverage is 61.42%. Comparing base (ce4469a) to head (6c14bbc).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5236      +/-   ##
==========================================
- Coverage   61.44%   61.42%   -0.03%     
==========================================
  Files         298      298              
  Lines       20824    20827       +3     
==========================================
- Hits        12796    12793       -3     
- Misses       7113     7120       +7     
+ Partials      915      914       -1     

[thaJeztah]

@laurazard first round of cleanup after the other one(s) 😄

[laurazard]

Looks great overall, thanks!

[thaJeztah]

Let me bring this one in 👍