When writing scripts for other shells, it can be confusing and annoying
that our `man` function shadows other manual pages, for example `exec(1p)`
from [Linux man-pages]. I almost never want to see the fish variant for such
contended cases (which obviuosly don't include fish-specific commands like
`string`, only widely-known shell builtins).
For the contented cases like `exec`, the POSIX documentation is more
substantial and useful, since it describes a (sub)set of languages widely
used for scripting.
Because of this I think we should stop overriding the system's man pages.
Nowadays we offer `exec -h` as intuitive way to show the documentation for
the fish-specific command (note that `help` is not a good replacement because
it uses a web browser).
Looking through the contended commands, it seems like for most of them,
the fish version is not substantially different from the system version.
A notable exception is `read` but I don't think it's a very important one.
So I think we should can sacrifice a bit of the native fish-scripting
experience in exchange for playing nicer with other shells. I think the
latter is more important because scripting is not our focus, the way I see it.
So maybe put our manpath at the end.
In lieu of that, let's at least have `exec.rst` reference the system variant.
[Linux man-pages]: https://www.kernel.org/doc/man-pages/Closes#10376
Recent synopsis changes move from literal code blocks to
[RST line blocks]. This does not translate well to HTML: it's not
rendered in monospace, so aligment is lost. Additionally, we don't
get syntax highlighting in HTML, which adds differences to our code
samples which are highlighted.
We hard-wrap synopsis lines (like code blocks). To align continuation
lines in manpages we need [backslashes in weird places]. Combined with
the **, *, and `` markup, it's a bit hard to get the alignment right.
Fix these by moving synopsis sources back to code blocks and compute
HTML syntax highlighting and manpage markup with a custom Sphinx
extension.
The new Pygments lexer can tokenize a synopsis and assign the various
highlighting roles, which closely matches fish's syntax highlighing:
- command/keyword (dark blue)
- parameter (light blue)
- operator like and/or/not/&&/|| (cyan)
- grammar metacharacter (black)
For manpage output, we don't project the fish syntax highlighting
but follow the markup convention in GNU's man(1):
bold text type exactly as shown.
italic text replace with appropriate argument.
To make it easy to separate these two automatically, formalize that
(italic) placeholders must be uppercase; while all lowercase text is
interpreted literally (so rendered bold).
This makes manpages more consistent, see string-join(1) and and(1).
Implementation notes:
Since we want manpage formatting but Sphinx's Pygments highlighing
plugin does not support manpage output, add our custom "synopsis"
directive. This directive parses differently when manpage output is
specified. This means that the HTML and manpage build processes must
not share a cache, because the parsed doctrees are cached. Work around
this by using separate cache locations for build targets "sphinx-docs"
(which creates HTML) and "sphinx-manpages". A better solution would
be to only override Sphinx's ManualPageBuilder but that would take a
bit more code (ideally we could override ManualPageWriter but Sphinx
4.3.2 doesn't really support that).
---
Alternative solution: stick with line blocks but use roles like
:command: or :option: (or custom ones). While this would make it
possible to produce HTML that is consistent with code blocks (by adding
a bit of CSS), the source would look uglier and is harder to maintain.
(Let's say we want to add custom formatting to the [|] metacharacters
in HTML. This is much easier with the proposed patch.)
---
[RST line blocks]: https://docutils.sourceforge.io/docs/ref/rst/restructuredtext.html#line-blocks
[backslashes in weird places]: https://github.com/fish-shell/fish-shell/pull/8626#discussion_r782837750
For builtins that have the same name as common commands, it might not
be entirely obvious that there is another page.
So, for those builtins, we add a note, but only in the man pages.
(exception is true and false because the note would be longer than the
page, and it's fridging true and false)
Fixes#8077.
