I'm about to make conflicts also get materialized in executable
files. We'll lose some of the test coverage in `test_chmod_command.rs`
then, because the those tests rely on the materialized content to
describe the executable bits. So this commit adds a debug command for
printing tree values and uses that in the tests.
I have used the tree-level conflict format for several weeks without
problem (after the fix in 51b5d168ae). Now - right after the 0.10.0
release - seems like a good time to enable the config by default.
I enabled the config in our default configs in the CLI crate to reduce
impact on tests (compared to changing the default in `settings.rs`).
`jj chmod` won't operate on conflicts involving non-files on the
positive sides. However, the error message says "None of the sides of
the conflict are files", which is not correct.
They are shown next to the change and commit id, since they are other names the
commit can be referred by.
The description is separated from the branches by a ` | ` when there are
branches, so that one can tell the branches from the description without color.
The result looks like this: 
