Add support for subcommands in __fish_man_page

[radomirbosak]

This PR adds a feature that after typing git add and pressing
alt+h, the manpage for git-add instead of git would be displayed.

The new logic takes the first argument which doesn't start with a dash
and tries to display manpage for command-argument; it falls back to
man command it the first try doesn't succeed.

Fixes #3618.

[faho]

This will now print an error when the commandline is empty.

There's a few ways to stop that, I think I prefer a set -q args[1]; or return above.

[radomirbosak]

You are right.. I didn't test the empty commandline scenario after adding basename.

I'm adding the check and additionally printing \a so that the behavior in case of empty commandline is consistent with other cases (non-existent manpage).

[faho]

What is the string join supposed to do here?

Also, the grep can be replaced with string match.

So: commandline -po | string match -rv '^-' should work.

[radomirbosak]

The string join \n was there because grep expects the tokens newline delimited, while commandline -po produces them space-delimited (maybe more precisely - it's that array-separator character).

In any case - your suggestion is simpler - so I'm changing the code to that.

[faho]

while commandline -po produces them space-delimited

It doesn't - it delimits with newline. Presumably whatever you tested this with changed the separator. I'd be interested to know what that was, since we don't want to be leaking \x1e (that "array-separator").

[radomirbosak]

Oh, my mistake.. I tested it with echo (commandline -po) | grep ... and didn't realize it was echo which was creating the spaces.

[faho]

Now that I've addressed the code, on to the general idea.

I'm actually suprised how well this rather simple approach works - so far I haven't found a case where it fails (well, it does with ip addr, but that's because the actual subcommand is "address" and "addr" is just a short form - not something that needs to be supported).

I'd be grateful if others could test this so that we don't have any embarrassing failures in obvious situations that I'm too dense to see.

[krader1961]

Looks okay to me. A problem with the original and new version of this function is that when I exit the man pager the command line isn't refreshed. Adding commandline -f repaint to the bottom of the function fixes it.

[radomirbosak]

@krader1961 Interesting, I don't have the issue you are describing. After exiting the man pager, the commandline is (visually) in the same state as it was before entering the man pager.

Which terminal are you using? I'm using gnome-terminal.

[radomirbosak]

Added commandline -f repaint to the bottom of the function.

[krader1961]

Added commandline -f repaint to the bottom of the function.

Thanks. The reason you don't need it, and probably most people, is that you're using less or another pager that switches to the alternate screen by default. I don't like that behavior so I put --no-init in my $LESS env var. Which means less scribbles on the screen containing the prompt for me. I've never bothered to fix this because I've only used [alt]H a couple of times when exploring what various key bindings do.

[krader1961]

Merged as commit f9835b5. Thanks.