diff to detect only case changes

Question

Is there a simple way to have a diff between two versions of a file, showing only those lines/words that differ by a change to upper-/lowercase? All other differences should be omitted.

Background: I have a VBA project under version control (git) and Microsoft's editor tends to change casing every time a new variable is declared. I want to identify (and possibly count) such changes in order to prevent them from being committed.

@LasseV.Karlsen This situation is not required to be recognized by the diff. — Nicolas Malebranche, May 18 '20 at 09:34
I'm guessing that writing such a difftool might not be too complex. I don't know of any already built that does just this. — Lasse V. Karlsen, May 18 '20 at 10:15
I'll see if I can whip up a small tool for you. If I can I'll put it on github so you can download the code and tweak it to your requirements. — Lasse V. Karlsen, May 18 '20 at 10:20
Here's a small tool you can try - https://github.com/lassevk/CaseDiff — Lasse V. Karlsen, May 18 '20 at 11:03
Apologies, if you already tried it I introduced a bug in rewriting some code, it should be fixed now. — Lasse V. Karlsen, May 18 '20 at 11:13
@LasseV.Karlsen That's a great tool you've written! I am adding it as a difftool — Nicolas Malebranche, May 20 '20 at 12:17

score 0 · Accepted Answer · answered Aug 06 '20 at 07:07

Based on a suggestion from this answer I have done it as follows, using basic Linux scripting tools:

GIT_EXTERNAL_DIFF='diff -p -U 0 "$2" "$5" | cat #' git diff --ext-diff >  cdiff
GIT_EXTERNAL_DIFF='diff -ip -U 0 "$2" "$5" | cat #' git diff --ext-diff > idiff

diff idiff cdiff | grep '^> [+-] '

The code makes first a case-sensitive diff cdiff, second a case-insensitive diff idiff. The case-only changes consist then of the lines in cdiff which are not contained in idiff.

diff to detect only case changes

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