lei rediff: fix construction of git-diff options

When generating git-diff options, lei-rediff extracts the single
character option from the lei option spec.  However, there's no check
that the regular expression actually matches, leading to an
unintentional git-diff option when there isn't a short option (e.g.,
--inter-hunk-context=1 maps to the invalid `git diff --color -w1').

Check for a match before trying to extract the single character
option.

Fixes: cf0c7ce3ce81b5c3 (lei rediff: regenerate diffs from stdin)

0 files changed, 0 insertions, 0 deletions