Re: [PATCH v2 4/8] pack-objects: add GIT_TEST_NAME_HASH_VERSION

> --name-hash-version=<n> option in 'git pack-objects'. This allows for
> extra testing of the feature without repeating all of the test
> scenarios. Unlike many GIT_TEST_* variables, we are choosing to not add
> this to the linux-TEST-vars CI build as that test run is already
> overloaded. The behavior exposed by this test variable is of low risk
> and should be sufficient to allow manual testing when an issue arises.
>
> But this option isn't free. There are a few tests that change behavior
> with the variable enabled.
>
> First, there are a few tests that are very sensitive to certain delta
> bases being picked. These are both involving the generation of thin
> bundles and then counting their objects via 'git index-pack --fix-thin'
> which pulls the delta base into the new packfile. For these tests,
> disable the option as a decent long-term option.
>
> Second, there are two tests in t5616-partial-clone.sh that I believe are
> actually broken scenarios. While the client is set up to clone the
> 'promisor-server' repo via a treeless partial clone filter (tree:0),
> that filter does not translate to the 'server' repo. Thus, fetching from
> these repos causes the server to think that the client has all reachable
> trees and blobs from the commits advertised as 'haves'. This leads the
> server to providing a thin pack assuming those objects as delta bases.
> Changing the name-hash algorithm presents new delta bases and thus
> breaks the expectations of these tests. An alternative could be to set
> up 'server' as a promisor server with the correct filter enabled. This
> may also point out more issues with partial clone being set up as a
> remote-based filtering mechanism and not a repository-wide setting. For
> now, do the minimal change to make the test work by disabling the test
> variable.
>
> Third, there are some tests that compare the exact output of a 'git
> pack-objects' process when using bitmaps. The warning that ignores the
> --name-hash-version=2 and forces version 1 causes these tests to fail.
> Disable the environment variable to get around this issue.
>