Re: does a successful 'git gc' imply 'git fsck'

On Sat, Dec 1, 2012 at 6:31 PM, Sitaram Chamarty [off-list ref] wrote:

Background: I have a situation where I have to fix up a few hundred
repos in terms of 'git gc' (the auto gc seems to have failed in many
cases; they have far more than 6700 loose objects).  I also found some
corrupted objects in some cases that prevent the gc from completing.

I am running "git gc" followed by "git fsck".  The majority of the
repos I have worked through so far appear to be fine, but in the
larger repos (upwards of 2-3 GB) the git fsck is taking almost 5 times
longer than the 'gc'.

If I could assume that a successful 'git gc' means an fsck is not
needed, I'd save a lot of time.  Hence my question.

Not really. For example fsck verifies that every blob when
decompressed and fully inflated matches its SHA-1. gc only checks
connectivity of the commit and tree graph by making sure every object
was accounted for. But when creating the output pack it only verifies
a CRC-32 was correct when copying the bits from the source to the
destination, it does not verify that the data decompresses and matches
the SHA-1 it should match.

So it depends on what level of check you need to feel safe.