Support diff-so-fancy patch mode by using `--patch` when building code sets

[scottchiefbaker]

I have Lazygit configured to use diff-so-fancy per your excellent documentation. I would love to see Lazygit support d-s-f while in patch mode also. If a user wants to include parts of a file in their commit they can run git add . --patch and d-s-f will highlight the patch pieces appropriately.

Is it possible for Lazygit to use --patch for it's internal patch mode text selection?

-- Scottchiefbaker / Diff-so-Fancy lead developer

[stefanhaller]

Hi Scott, sorry for not responding earlier.

Is it possible for Lazygit to use --patch for it's internal patch mode text selection?

Yes, this might be possible. It would require adding a separate pager config to lazygit that is used only for the staging panel. Lazygit would then have to run the diff twice, once without pager for the internal patch logic, and again with the pager for display; it could verify that the number of lines returned by each is the same, to double-check that users didn't forget the --patch option (or --color-only if they are using delta). It seems that git add -p makes the same check, because it shows an error if I set interactive.diffFilter to diff-so-fancy without --patch.

It's not an easy change though; I remember that I briefly looked into it a while ago, and found it to be more effort than I was willing to spend at that time. I might look into it again when I find the time, but I'm also happy to support anyone who wants to give it a try.

[scottchiefbaker]

The more I think about it... you may not even need our --patch mode. A simple git diff in diff-so-fancy output would be sufficient if you break the chunks up in lazygit.

All git add --patch does is get you the "y/n/s" options for each chunk. Lazygit does that all internally.

[stefanhaller]

Yes, --patch is needed in lazygit, same as on the command line. It makes sure that the pager's output matches the raw diff exactly, which is important for git or lazygit to do their job.

Here's a very preliminary draft PR if you want to play with it: #4332. See the PR description for what's missing.