Autoscroll colorify compiler output

[psprint]

Hi,
I think that this PR implements quite a valuable features, which all converge to a very useful use case (explained at the end). The features are:

The patches

1. Autoscroll of the pager view – quite a missed feature, with a protection against overactivity – the view has to be placed at the bottom for the autoscroll to occur – i.e.: it's safe to scroll up and have a stable view of what's going on.

2. Colorizing of the compiler's errors and warnings (and notes) in pager view.
   The errors are to be browsed in the use case explained below, so they are being colorized first here by this patch.

The use case

The two patches open a way for a configuring of TIG as a comfortable IDE-like errors round-trip fixing tool, by:

1. Configuring the 'n' key in pager to search for lines with "error:|warning:|note:" regex, via.:

   bind pager n :/warning:|error:|note:
   

2. Configuring Return in pager to open the editor on the line number extracted from the current error/warning/note, via:

   bind pager <Enter> !sh -c "~/github/tig/contrib/make-line-open.zsh '%(text)'"
   

3. Optionally, configuring 'E' to run :!make, via:

   bind generic E :!make
   

4. Setting the compiler-msg color (the only thing that's problematic - I don't know how to make a default value for it), via:

   color compiler-msg yellow default bold
   

Then what's possible is the following use case: .

Helper script body

The make-line-open script is as follows:

#!/usr/bin/env zsh

emulate zsh -o extended_glob

if [[ $1 == (#b)([^:]##):([0-9]##):* ]]; then
    [[ -z $EDITOR ]] && EDITOR=mcedit

    $EDITOR +$match[2] **/$match[1]
fi

Summary

The patches are quite simple, only 9 and 21 lines and follow the coding style. I think that the patches are useful also without/outside the use case – having pager view autoscrolled, for example, is an useful thing.

[psprint]

Does this PR have a chance of a merge, @koutcher ? I see no merges of PRs in this project. But because of quality of the code and its compactness, maybe you could merge? The patch can be seen/verified from inside out, that's small it is.

[krobelus]

Thanks for sharing but this seems quite specific to your use case.
The autoscroll feature should not be active by default - Tig is emulating less.
Autoscrolling makes a :!git log deviate from less.

[krobelus]

I think you'd need to call regfree to avoid a memory leak

[krobelus]

This is really specific. I think this should either be handled by a user-settable regex, or by an external program.
We could teach Tig to preserve ANSI escape codes in the output, then something like :!ls --color would work as well.

[koutcher]

Thanks for your contribution. I tend to agree with Johannes on the specificity of the use case, especially we shall not embed hardcoded patterns. I'll leave it to Jonas to decide.

[psprint]

In a few days I'll provide an updated patch that will address the points, e.g.: will use an option for the regex.

[koutcher]

Superseded by #1223 and #1249.