[RFC PATCH 0/3] range-diff: treat notes like `log`

[Kristoffer Haugsbakk <code@khaugsbakk.name>]

Currently, `range-diff` shows the default notes if no notes-related
arguments are given. This is also how `log` behaves. But unlike
`range-diff`, `log` does *not* show the default notes if
`--notes=<custom>` are given.

These changes are supposed to make `format-range` behave like `log` with
regards to notes.

These changes also fixes an issue with notes being shared in the cover
letter via `range-diff`, and that’s really the main motivation for
making these changes.

§ How `log` works

`log` shows the default notes if no notes arguments are given. But if
you give it specific notes to show then it forgets about the default
notes. Further, there is the convenience `--notes` option which will
show the default notes again. These options are cumulative. For example:

    git log --notes --notes=custom

Will show the default notes as well as the `custom` notes.

See discussion in: https://lore.kernel.org/git/20110329143357.GA10771@sigill.intra.peff.net/

§ How `range-format` works

`range-format` passes `--notes` to `log`, which means that it does not
have the default behavior of `log` (forget the default logs if you say
e.g. `--notes=custom`). However, the man page says that (under
`--[no-]notes[=<ref>]`):

> This flag is passed to the git log program (see git-log(1)) that generates the patches.

This makes me (at least) think that `range-format` is supposed to work
just like `log` with regards to notes.

§ `format-patch` and the difference between showing and sharing

`format-patch` has a different default: it shows no notes. This makes
sense in my opinion since `format-patch` is meant to be used to share
changes with others, and you might be surprised if your notes (which
might have only been notes to yourself) are sent out in your emails
(keep in mind that notes refs are *not* pushed by default).

But the slightly faulty behavior of `range-diff` bleeds through to
`format-patch` since the latter calls the former; if you have default
notes they can be shared in the range-diff on the cover letter, even
though `format-patch` isn’t supposed to show them.

§ Code layout and approach to the problem

As I’ve said, my focus was on fixing `format-patch`, so I’ve considered
how `format-patch` calls `range-diff` which in turn calls `log`.

`format-patch` is a command which is defined in `builtin/log.c`. For
notes in particular it in fact has some explicit logic for handling
notes based on the value of `rev`. (There seems to be no issues with
this part of the code; only the code in `range-diff.c` which passes the
default argument to `log`.) It then calls
`range-diff.c:show_range_diff`. That function on `master` loads some
default arguments, among them `--notes`. It then eventually calls `log`
as a subprocess.

My change consists of co-opting the deprecated `--standard-notes` and
changing its behavior so that it can be used in
`range-diff.c:show_range_diff`.

Using a special switch/option was the only way I found in order to fix
this problem.

I could have also created a new option but I thought that doing a
smaller change initially would be better.

§ RFC

This is marked as RFC since I chose to co-opt a deprecated option in
order to get `range-format` to work, in my opinion, as it should.

§ Carbon copy

Based on `contrib/contacts/git-contacts master..@`.

Kristoffer Haugsbakk (3):
  range-diff: treat notes like `log`
  doc: pretty-options: remove documentation for deprecated options
  revision: comment `--no-standard-notes` as deprecated

 Documentation/pretty-options.txt |  1 -
 range-diff.c                     |  2 +-
 revision.c                       |  8 ++++++--
 t/t3206-range-diff.sh            | 28 ++++++++++++++++++++++++++++
 4 files changed, 35 insertions(+), 4 deletions(-)

-- 
2.41.0.rc2