How --default-language option works?

[alefbragin]

Some times delta cannot infers language from a filename. And it is pretty obvious that --default-language targets this cases:

        --default-language <default-language>
            Default language used for syntax highlighting when this cannot be inferred from a filename. It will
            typically make sense to set this in per-repository git config (.git/config)

But I try to utilize it in several ways, and neither is successful.

git config delta.default-language 'Bourne Again Shell (bash)'
git diff

git -c delta.default-language='Bourne Again Shell (bash)' diff

delta --default-language 'Bourne Again Shell (bash)' file1 file2

Moreover there are open feature requests with similar purposes: #485, #499. Do I correctly understand purpose of the option? Or maybe the option is buggy?

[dandavison]

Hi @alefbragin, I'm sorry, you hit upon an option which I had introduced for one purpose, but not announced, and was not doing what one would expect. I've fixed that now in #859 (so if you can compile Rust and would like to test that branch then great!). Here's what I wrote there:

The default-language option had been introduced initially in order to determine language for git blame (where there are no file names). However, subsequently git blame came to determine the language by inspecting the command line of the calling process (e.g. if delta sees the calling process is git blame src/file.ts then the language is typescript). Meanwhile default-language never actually acquired its obvious function of providing a default language for diffs; this PR fixes that.

Note that the best place to set default-language is probably in your per-repository git settings. I.e. $my_repo/.git/config.

[alefbragin]

Hi @dandavison! Thanks for the great utility and for the fix! I build that branch and it works as expected in my cases.
I think the fix helps @zachriggle in the case.
And this commit possibly close #499 because this is exactly what was requested, but author of request needs it for bash's process substitution (<(...)) that doesn't work with delta.

[eitau]

@dandavison can you specify that currently default-language option only applies to blame and, as far I can tell, grep subcommands in the cli's help output? I just got quite frustrated trying to debug why it isn't working in general case for past hour. Cheers

[dandavison]

The argument to default-language is a file extension, without the . So for example, this works on that branch:

git -c delta.default-language=bash diff

or

git -c delta.default-language=sh diff

Or, add to per-repository git config ($myrepo/.git/config):

[delta]
    default-language = bash # or "sh"