This was spawned by a mailing list discussion. I'm going to summarize what I think is the conclusion of that discussion:

• stack install is a misnomer, since this is just about copying an executable to a new directory
• As such, we should ideally rename the command to stack cp or similar
• However, many users will expect a stack install command to exist
• So: we'll add a stack cp command with the exact behavior of stack install today, and modify stack install to (1) give a message "you probably meant stack cp" (possibly with a link to this very issue?) and then perform a stack cp

If we go this route, I imagine we should do something quite similar for stack uninstall, but that's really a separate discussion.