Support diff -u ... | delta

[fdcds]

It would be nice if diff -u ... | delta was supported. Currently delta does not appear to parse the header correctly and instead passes on some garbage:

❯ diff -u a b | delta
diff -u a/file b/file
--- a/file      2019-11-12 19:33:40.199834121 +0100

file    2019-11-12
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
+++ b/file      2019-11-12 19:33:54.767769647 +0100

1
 a                                                                                                                                                                                                                                                                                                                                                                                                                                       
 b                                                                                                                                                                                                                                                                                                                                                                                                                                       
 c                                                                                                                                                                                                                                                                                                                                                                                                                                       
 x                                                                                                                                                                                                                                                                                                                                                                                                                                       
   a                                                                                                                                                                                                                                                                                                                                                                                                                                     
   b                                                                                                                                                                                                                                                                                                                                                                                                                                     
   c                                                                                                                                                                                                                                                                                                                                                                                                                                     
 y                                                                                                                                                                                                                                                                                                                                                                                                                                       
 iff -u a/file2 b/file2                                                                                                                                                                                                                                                                                                                                                                                                                  
--- a/file2     2019-11-12 19:40:49.344885714 +0100

file2   2019-11-12
─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
+++ b/file2     2019-11-12 19:40:54.800860547 +0100

1 
 1                                                                                                                                                                                                                                                                                                                                                                                                                                       
 2   

Note how the diff command for file2 even lost its first character. (It actually displays like that and is not a copy & paste mistake by me.)

Using delta version 0.0.14.

[dandavison]

Thanks, absolutely agree this makes sense. (Indeed it makes me uncomfortable that the package name is git-delta seeing as I would like it to support standard unified diff when not embedded in git output.)

Incidentally, this would make a good issue for anyone looking for a smallish Rust exercise.

[m-lima]

I'm pretty new to Rust and I would like to start contributing to OSS. Do you mind if I take a stab at this?

[dandavison]

@m-lima That would be great, thanks very much! Feel free to discuss further / ask me any questions.

[m-lima]

Thanks @dandavison, I will get started on it

@fdcds I wasn't able to really replicate the problem on version 0.0.14
I tried it on Ubuntu and Catalina.
However, I did notice an assumption of a/<file_name_1> and b/<file_name_2> from git --diff. But that the most of a weird behavior I got

[m-lima]

I understood the situation now. It is more accentuated when comparing directories, and you have multiple file headers.
Pushing a commit to assess that as well, by adding a new state that captures diff -u or diff -U

[dandavison]

This is fixed in master, including handling of unified diff directory comparisons, thanks to work by @m-lima: #56.

[fdcds]

Thanks a lot to both of you!