Fix _forgit_diff on macOS

[sandr01d]

Check list

• I have performed a self-review of my code
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation

Description

In bash 3.2 uninitialized arrays contain one entry: an empty string, whereas in modern versions of bash they do not contain any entry. I could not find documentation on this but the behavior can be verified by running the following script:

local arr
echo "length=${#arr[@]}"
echo "content=${arr[@]}"

On bash 5.2.26 this prints

length=0
content=

On bash 3.2.57 this prints

length=1
content=

This PR makes sure the $commits and $files arrays are explicitly initialized as empty arrays to allow git to fall back to diffing local changes instead of trying to diff against a revision with a name of an empty string.

Fixes #373

Type of change

• Bug fix
• New feature
• Refactor
• Breaking change
• Documentation change

Test environment

• Shell
  • bash
  • zsh
  • fish
• OS
  • Linux
  • Mac OS X
  • Windows
  • Others:

[sandr01d]

Since this is a regression from #326, I'd like to merge this before the release next week.

[cjappl]

This still works with mac and fish 👍

It appears I also have the newer version of bash, so that's why we hadn't seen it before. Thanks for the quick fix.

[keatsfonam]

FYI this still doesn't work with bash 3.2: #373 (comment)

[sandr01d]

Thanks for the hint with the bash docker container @keatsfonam, this helped me track it down. Will keep that in mind for future issues. I got it working in bash 3.2 in the container. Could you give it another try?

[cjappl]

Passes both fish with newer bash (5.2) and in the docker container for me.

OK to merge once the reporting user says it's all good!

[keatsfonam]

@sandr01d new fix works for me, thank you