read-cache.c: drop PROT_WRITE from mmap of index
Once upon a time, git's in-memory representation of a cache entry actually pointed to the mmap'd on-disk data. So in 520fc241 (Allow writing to the private index file mapping., 2005-04-26), we specified PROT_WRITE so that we could tweak the entries while we run (in our own MAP_PRIVATE copy-on-write version, of course). Later, 7a51ed66 (Make on-disk index representation separate from in-core one, 2008-01-14) stopped doing this; we copy the data into our in-core representation, and then drop the mmap immediately. We can therefore drop the PROT_WRITE flag. It's probably not hurting anything as it is, but it's potentially confusing. Note that we could also mark the mapping as "const" to verify that we never write to it. However, we don't typically do that for our other maps, as it then requires casting to munmap() it. Signed-off-by: NJeff King <peff@peff.net> Signed-off-by: NJunio C Hamano <gitster@pobox.com>
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