Junio C Hamano [off-list ref] writes:

quoted

...Thanks, for pointing this out. Also, in the above method for
alnum I think we can initialize an array of alnum[] instead of
alphas[]. Or otherwise I was thinking to instead check:
           if (!isalnum(*c) && *c == ':')

Sure a loop is fine, or alnum[] is fine, or just alpha[] is OK, I
would think.  Do you foresee you'd need --fixup=chomp124:<commit>?
I somehow doubt it.

Having said that, we may regret if we did not include some
punctuation to allow for a multi-word keyword.  IOW, "alpha plus
dash" might be a reasonable minimum.

But what keyword --fixup=<keyword>:<commit> can take is entirely
under our control, so it is not all that unreasonable if we just
forced our developers some discipline to pick a single-word keyword
for any of their future enhancements.  It's not like we are opening
up extensibility to the end-users, who may complain that the way
they can spell their new <keyword> is too limited.  So if we already
have alpha[] and/or a helper function that does strspn(alpha) that
we can reuse elsewhere, I do not think it is worth to try supporting
punctuation.

Thanks.