Allows:
* self.commit()
* self.line_number()
* self.first_line_in_hunk()
Certain pagers (like `delta`), when used for `git blame`, only show the
commit information for the first line in a hunk. This would be a nice
addition to `jj file annotate`.
`jj file annotate` already uses a template to control the rendering of
commit information --- `templates.annotate_commit_summary`. Instead of
a custom CLI flag, the tools necessary to do this should be available in
the template language.
If `1 % 2` or `1.is_even()` was available in the template language, this
would also allow alternating colors (using `raw_escape_sequence`).
Example:
```toml
[templates]
# only show commit info for the first line of each hunk
annotate_commit_summary = '''
if(first_line_in_hunk,
show_commit_info(commit),
pad_end(20, " "),
)
'''
```
With this change a warning is shown if the user does not explicitly specify the target revision, but the behavior is unchanged (it still defaults to the working copy).
In the future the warning will be turned into an error. In other words, it will be required to specify target revision.
The bulk of the changes here are to prepare tests for the upcoming change, to make the transition easier.
For additional details please see:
* https://github.com/jj-vcs/jj/issues/5374
* https://github.com/jj-vcs/jj/discussions/5363
The problem is that author names are variable-length by nature, and format_*()
can be customized in that way. Commit ids are redundant in most cases where
commits aren't diverged.
We could add some format_short_fixed_length_*() hook points, but it would
probably be easier to just customize the annotation template at all.
