Well-Known Tool Configurations

[halostatue]

I wonder if it would be worthwhile adding support for well-known tool configurations. The default configuration for merge is vimdiff and the default configuration for diff is diff -u, but I wonder if it would be worthwhile to make it easier to support specific tools like Emacs, VS Code, Meld, Kaleidoscope, Beyond Compare, etc. Maybe instead of merge.command it would be merge.tool with a string-enum value that holds those. Or we add a new section to the documentation with configurations for those.

This is inspired by #3279, but is not wholly restricted to just diff and merge, although those are the only ones that I can think of because I just replied to that one.

The biggest argument against this would be deciding when a new tool would justify being added to either the .tool list or documentation. We don't necessarily want to support All The Tools, just the ones that are more likely to be used than not.

[twpayne]

Hmm, I think it would be sufficient to provide examples in the documentation of how set merge.command and merge.args for each tool. I don't think there needs to be any code change to chezmoi to support the different tools.

At a higher level, I'm keen that chezmoi provides mechanism, not policy. For example, chezmoi provides a mechanism to plug in external diff and merge tools, but (other than having sensible defaults) no policy limiting your choice of tool.

[halostatue]

Yes, it would be sufficient to document, but offering a merge.tool configuration would not necessarily be dictating policy so much as providing multiple named sensible defaults.

Nothing says that I couldn’t do merge.tool = "emacs" and merge.command = "emacsclient". (It would make much less sense to provide a merge.args override in this case.)

I think that part of what I’m suggesting is an opportunity to make certain well-known configurations like this extensible.

Also, as an alternative, it might be nice to be able to do something like git does with mergetool:

merge:
  tools:
    ksdiff:
      command: ksdiff
    emacs:
      command: emacs
      args: …

Then we could do chezmoi merge --tool=emacs or something similar so that I could support both command-line and GUI diffing or merging. This would be similar, I suspect with other external helper tools (pager, etc.).

[Lockszmith-GH]

(Hope it's ok to butt in):
How about letting git's configuration be the default behavior for chezmoi?

[halostatue]

I would probably be against this because git simply has cmd with environment variables as its parameters:

[difftool "Kaleidoscope"]
  cmd = "/usr/local/bin/ksdiff" --partial-changeset --relative-path "${MERGED}" -- "${LOCAL}" "${REMOTE}"

[mergetool "Kaleidoscope"]
  cmd = "/usr/local/bin/ksdiff" --merge --output "${MERGED}" --base "${BASE}" -- "${LOCAL}" --snapshot "${REMOTE}" --snapshot
  trustExitCode = true

Transforming that would be something of a pain, especially as chezmoi's triple for 3-way merge is (Target,Source,Destination) instead of (Remote,Local,Base). The Destination isn't quite the same as Base or Merged.