Stablize `App::replace` Tracking Issue

[epage]

Original request: #1603

Original PR: #1697

Feature flag: unstable-replace

Known issues:

• Help subcommand behaves different than help flags when App::replace is used #2011
• No presence in --help

[pksunkara]

We should link implementation also, right?

[epage]

Works for me.

[pksunkara]

So -l expands to --source list and -r expands to --target residues?

The unstable replace feature gets you part way. It would allow a -l to expand out but it wouldn't allow -lr.

Another issue with this feature as the use case is documented here