Thomas Gummerer authored Jul 14, 2018 and Junio C Hamano committed Jul 16, 2018

We have multiple different variants of the error message we show to
the user if 'read_cache' fails.  The "Could not read index" variant we
are using in 'rerere.c' is currently not used anywhere in translated
form.

As a subsequent commit will mark all output that comes from 'rerere.c'
for translation, make the life of the translators a little bit easier
by using a string that is used elsewhere, and marked for translation
there, and thus most likely already translated.

"index file corrupt" seems to be the most common error message we show
when 'read_cache' fails, so use that here as well.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>