Ignore whitespace for only certain file extensions when merging

Question

I have this command

git merge -Xignore-all-space origin/dev

scares me a little bit b/c I am afraid of merging a file where whitespace matters. Is there a way to limit it to certain files, something like this:

git merge -Xignore-all-space *.js origin/dev

Answer 1

Anytime you want to set a configuration per file extension, a good place to start is gitattributes.
In a .gitattributes files, you can set a directive per file, or per file extension.

However, the *.js -whitespace I mentioned in 2009 might not apply during a merge.

Since ignore-all-space is first a git diff option, you might need to set up a diff driver in a .gitattributes (again, only for *.js files), emulating --word-diff-regex

Use <regex> to decide what a word is, instead of considering runs of non-whitespace to be a word

Every non-overlapping match of the is considered a word. Anything between these matches is considered whitespace and ignored(!) for the purposes of finding differences.

You may want to append |[^[:space:]] to your regular expression to make sure that it matches all non-whitespace characters. A match that contains a newline is silently truncated(!) at the newline.

For example (to be tweaked in order to match what you need in a javascript file for a diff without spaces)

*.js    diff=js
[diff "js"]
    wordRegex = "[^[:space:]]+"