When running arc diff with untracked files in the repo, we get this message:
Do you want to amend these files to the commit? [y/N]
But when running arc land with the same files in the repo, this is the message:
Do you want to continue without adding these files? [Y/n]
Why not use the same question and default for both?
The reason to not use the same language and defaults for both is they are different operations.
arc diff submits changes for review. in theory, you want to add all the changes, or at least might want to such that this question is best. Note though the default to "no", assuming the engineer knows what they were doing in preparing the changes for review, i.e. if using git they properly "git add"ed files as they wanted. Also note users might have scratch files from editors, etc that they really don't want to submit for review.
arc land is used to submit reviewed changes, warning heartily if the changes haven't been reviewed. changes that aren't in the diff aren't reviewed by definition. in theory, you don't want to land unreviewed changes, because otherwise, what is the point of code review? Again, note the default assuming savvy engineer usage relative to the flow. The same scratch file thing could likely be in place too.
Letting this live on (at least for now) in T4163. Feel free to add thoughts / comments over there.