Word-diff feature

[MisanthropicBit]

First draft of the word-diff feature, implementing #66. Word-diff mode is toggled via r and R (as in wo[r]d-diff)

Tests pass locally with vim-themis using both vim v8.2 and v0.4.4, although there are 2 pending tests (41 and 42) with vim with the message: "# width of preview window cannot be changed" which makes sense since they are skipped if we don't have neovim 0.4.

Docs and syntax files have been updated as well. Hopefully this is close to the desired implementation but please provide some feedback if not 🙂

EDIT: There is something fishy going on with the action-setup-vim and the command sudo apt install -y vim-gnome. Not sure what the problem is but I'll try to investigate. Perhaps it has something to do with the fact that GitHub Actions recently upgraded ubuntu-latest to 20.04.1 LTS from 18.04.5 LTS.

[rhysd]

Thank you for adding this! I'll check CI

[rhysd]

@MisanthropicBit I added workaround for CI failure. Could you rebase this branch onto master? https://github.com/rhysd/git-messenger.vim/actions/runs/530931012

[MisanthropicBit]

@rhysd Thanks for fixing the CI workflow. All checks passed :)

I still need to add some feature-specific tests to all.vimspec. If you think this looks good so far, I'll go ahead and add some tests similar to those for d and D.

[rhysd]

I'm sorry for the delay. I needed to fix action-setup-vim since ubuntu-latest recently transitioned to Ubuntu 20.04. Now I'm starting to review this.

[rhysd]

@MisanthropicBit I'm playing with this feature. What do you think about hiding [-,-],{+,+} markers by conceal?

[MisanthropicBit]

I'm sorry for the delay. I needed to fix action-setup-vim since ubuntu-latest recently transitioned to Ubuntu 20.04. Now I'm starting to review this.

Take the time you need 🙂 I'm glad my suspicion about ubuntu-latest was well-founded.

I really like concealing the markers! Removes a lot of visual clutter and seems like a sensible default. Perhaps it should be configurable via an option but since the highlighting makes everything pretty clear, perhaps not?

[rhysd]

@MisanthropicBit Thank you for your thoughts. I think providing option for concealing is better. I'll add it after merging this PR.