🚀 use diff-compatible exit statuses that differ between difference-found and error

[calestyo]

🚀 use diff-compatible exit statuses that differ between difference-found and error

[dandavison]

Hi @calestyo, I thought that it worked like that already! Can you post an example? This is MacOS in zsh.

~ delta <(echo a) <(echo a) > /dev/null; echo $?
0
~ delta <(echo a) <(echo b) > /dev/null; echo $?
1
~ delta <(echo a) __not_there__ > /dev/null; echo $?
diff: __not_there__: No such file or directory
2

[calestyo]

Indeed. Not sure how I produced the contradicting result.... I've been calling delta from a shell script, and I think there might have been an exit 1 at a wrong point, which has overridden delta’s 2.

Sorry for the noise.

btw: Is there a way in delta to disable colour output?

[dandavison]

No worries.

btw: Is there a way in delta to disable colour output?

You mean, keep all the reformatting and decorations but specifically disable colour? I don't think there is a way to do that, although perhaps there are enough colour settings in delta to achieve it piecemeal!

So in a script the answer would be not to call delta if one only wants the raw git/diff input, and of course, git doesn't invoke delta at all if output is not a tty. But if you explicitly pipe to delta in a script then it will add colours and text decorations / reformatting.

[calestyo]

No worries.

I reproduced it... wait a second...

[calestyo]

$ touch foo
$ stat /tmp/bar
stat: cannot statx '/tmp/bar': No such file or directory
$ delta foo /tmp/bar ; echo $?
error: Could not access '/tmp/bar'
1

If I do however:

$ delta <(echo foo) /tmp/bar ; echo $?
diff: /tmp/bar: No such file or directory
2

[dandavison]

Ah-ha, I'm not at my computer but I do remember that the code handling process substitutions had to do something unfortunate. Feel free to investigate!

[calestyo]

There are more cases:

$ delta /dev/null non-existent
$ delta /dev/random non-existent
$ delta /dev/uinput non-existent

all give 1, and only uinput is permission-wise not accessible by the user.

Also:

$ ln -s /nonexistent dangling.symlink
$ delta dangling.symlink non-existent

Though it works when comparing with an existent file (not sure, btw. whether it should even then, cause then there's still one inaccessible file - the target of the dangling symlink).

[calestyo]

Also when doing using a directory as existent file:

$ delta /tmp non-existent

[calestyo]

That issue may even go yet a bit further.

Assume I do:

foo="$(diff -u a b)"

(and there is a difference)

and then:

printf '%s\n' "$foo"  |  delta

I get the differences shown, but exit status is 0 (and not 1).

[dandavison]

That's right, in something | delta delta behaves like cat or bat -- it's just a pager displaying stuff and exit code is 0 unless something goes wrong. On the other hand in delta a b delta acts as a diff program, and exit codes are as diff.

[calestyo]

Well unless for the other cases mentioned above, where one does have delta a b style and it still doesn't act like diff. :-)