Feature request: "dry run flags" for shell commands

[BatmanAoD]

In dry-run mode, Knope prints shell commands that would be run, but does not actually run them.

In some cases, the CLI tool that Knope is invoking has its own "dry-run" mode, and it would be useful to run that to validate that the command being run is correct.

I suggest something like:

[[workflows.steps]]
type = "Command"
dry_run_flag = "--dry-run"
command = "git push -o ci.skip"

...and the resulting command when running knope release --dry-run would be git push -o ci.skip --dry-run, which would be both printed and executed.

One problem with this is that there are probably tools where adding the flag at the end doesn't work, so perhaps there could be a "magic" $dryrun variable to handle more complex cases:

[[workflows.steps]]
type = "Command"
shell = true
dryrun = "--dry-run"
command = "git push $dryrun -o ci.skip && git push $dryrun -o ci.skip --tags""

Here, $dryrun would be empty unless --dry-run is passed to Knope, and set to --dry-run otherwise.