We were actually talking about this for quite a while on Discord yesterday. The duality is visible to the user in jj as least as much as it is in git.
Some command arguments treat commits as snapshots (e.g. `jj restore --from/--into`, `jj diff --from/--to`, `jj file list -r`) and some commands arguments instead inspect the diffs (e.g. `jj rebase -r/-b/-s`, `jj diff -r`, `jj squash --from`, `jj log <path>`).
The first-class conflicts (https://jj-vcs.github.io/jj/latest/conflicts/) allow jj to be much better at treating commits as diffs than git is. In particular, there's no real difference between merge commits and other commits; any commit can introduce conflicts and any commit can resolve conflicts. We define the changes in a commit as relative to the auto-merged parents. That means that the diff-centric command arguments work in a consistent way for merges too. For example, if you create a new merge commit (`jj new A B ...`), it might have conflicts, but we still consider it empty/unchanged. If you resolve the conflicts, then `jj diff` will show you the conflict resolutions, and `jj rebase` will rebase the conflict resolutions (a bit like git rerere, but it also works on hunks outside of the conflict areas).
Some command arguments treat commits as snapshots (e.g. `jj restore --from/--into`, `jj diff --from/--to`, `jj file list -r`) and some commands arguments instead inspect the diffs (e.g. `jj rebase -r/-b/-s`, `jj diff -r`, `jj squash --from`, `jj log <path>`).
The first-class conflicts (https://jj-vcs.github.io/jj/latest/conflicts/) allow jj to be much better at treating commits as diffs than git is. In particular, there's no real difference between merge commits and other commits; any commit can introduce conflicts and any commit can resolve conflicts. We define the changes in a commit as relative to the auto-merged parents. That means that the diff-centric command arguments work in a consistent way for merges too. For example, if you create a new merge commit (`jj new A B ...`), it might have conflicts, but we still consider it empty/unchanged. If you resolve the conflicts, then `jj diff` will show you the conflict resolutions, and `jj rebase` will rebase the conflict resolutions (a bit like git rerere, but it also works on hunks outside of the conflict areas).