Provide an option to cycle through delta themes using --show-themes

[clnoll]

When delta is invoked with --show-themes, cycles through all themes in the git config, where a theme is identified as a section with a "dark" or a "light" entry. Uses the computed is_light_mode value to determine whether to show light themes or dark themes by default.

When either the --dark or --light flag is passed in with --show-themes, will additionally display the dark or light themes, respectively. When --light and --dark are passed in, shows all themes.

The user can navigate from theme to theme using the n and N navigation keys.

In addition to viewing the themes using a sample diff, users can display themes on their own diff by piping it into delta, e.g. git show | delta --show-themes.

That being said, I might still swap out the sample commits used in the display, if I find something that seems to exhibit the themes' characteristics more clearly.

I'd also like to add a light theme or two to themes.gitconfig, because right now it only has dark themes to display.

[dandavison]

This is fantastic! Delta should definitely have this. Some tiny comments but I can see this is pretty close.

[dandavison]

Let's display them in alphabetical order.

[clnoll]

Done.

[dandavison]

Shall we use one of the example diffs used in the README, or something else? I was going to say we should choose a shortish one, but I can see the attraction in using a diff long enough to not fit on the screen -- i.e. that it prevents the user from seeing two themes on the screen at the same time.

[clnoll]

👍 I switched to vuejs/vue@7ec4627, from the README.

[dandavison]

Almost there! I think just selecting the default diff is all that remains.

[dandavison]

Excellent, thank you! Everything looks good. Hopefully your work here will lead to some really good themes being surfaced from delta users. (I added a link to the README section on themes to your --show-themes help text to try to help discoverability a bit more.)

[michaelblyons]

[09:37:44 ~]$ delta --version
delta 0.7.1
[09:37:53 ~]$ delta --show-themes
Pattern not found  (press RETURN)

Am I doing something wrong?

[dandavison]

Hi @michaelblyons, thank you, I don't think this is your fault. This is likely to be a bug, related to #237. Could you tell us the following information if you don't mind:

• operating system
• output of env | grep -i less
• output of env | grep -i pager
• output of less --version
• Contents of ~/.local/share/delta/lesshst if it exists

[michaelblyons]

• operating system

  • MacOS 11.2.3

• output of env | grep -i less

  • Nothing (and non-zero return code)

• output of env | grep -i pager

  • Nothing (and non-zero return code)

• output of less --version

  • less 487 (POSIX regular expressions) (text continues)

• Contents of ~/.local/share/delta/lesshst if it exists

  .less-history-file:
  .search
  "-b
  "alias
  "quiet
  "cert
  "-K
  "-k
  "--no
  "^Theme:
  

[dandavison]

Would you mind trying a more recent less? I'm assuming which less gives you /usr/bin/less. If you use homebrew could you do brew install less? (I'm not sure this is the problem.)

[dandavison]

Oh! I'm sorry, I know what the problem is. You need to tell delta where the themes are, like this: https://github.com/dandavison/delta#custom-color-themes

And for our part, we need to fix it so that it gives a more helpful error message!

[dandavison]

This bit is the key:

--

To use the delta themes, clone the delta repo (or download the themes.gitconfig file) and add the following entry in your gitconfig:

[include]
    path = /PATH/TO/delta/themes.gitconfig

[michaelblyons]

Oh, good. I was having some trouble with less, wherein which less suggested I was using a newly brew installed 563, but less --version still showed 487 (vs /usr/local/bin/less --version showing 563).

[dandavison]

Great, I'm glad it was nothing more serious than that. I wonder whether, in addition to that error message needing to be improved, this is pointing to moving some of the theme definitions into the executable itself. [The delta repo can continue to host a faster-evolving expanded collection, and users would still be able to create custom themes using [delta "my-theme"] either in ~/.gitconfig or in an include'd file.]