On Mon, May 20, 2024 at 04:14:29PM -0700, Junio C Hamano wrote: > A change recently merged to 'next' stops us from defaulting to using > SHA-1 unless other code (like a logic early in the start-up sequence > to see what hash is being used in the repository we are working in) > explicitly sets it, leading to a (deliberate) crash of "git" when we > forgot to cover certain code paths. > > It turns out we have a few. Notable ones are all operations that > are designed to work outside a repository. We should go over all > such code paths and give them a reasonable default when there is one > available (e.g. for historical reasons, patch-id is documented to > work with SHA-1 hashes, so arguably it, or at least when it is > invoked with the "--stable" option, should do so everywhere, not > just in SHA-1 repositories, but in SHA-256 repository or outside any > repository). In the meantime, if an end-user hits such a "bug" > before we can fix it, it would be nice to give them an escape hatch > to restore the historical behaviour of falling back to use SHA-1. > > These patches are designed to apply on a merge of c8aed5e8 > (repository: stop setting SHA1 as the default object hash, > 2024-05-07) into 3e4a232f (The third batch, 2024-05-13), which has > been the same base throughout the past iterations. > > In this fifth iteration: > > - The first step no longer falls back to GIT_DEFAULT_HASH; the > escape hatch is a dedicated GIT_TEST_DEFAULT_HASH_ALGO > environment variable, but hopefully we do not have to advertise > it all that often. > > - The second step has been simplified somewhat to use the "nongit" > helper when we only need to run a single "git" command in t1517. > The way the expected output files were prepared in the previous > versions did not correctly force use of SHA-1 algorithm, which > has been corrected. The third step and fourth step for t1517 > continue to be "flip expect_failure to expect_success", but you > can see context differences in the range-diff. > > - The fourth step also has a fix for t1007 where the previous > iterations did not correctly force use of SHA-1 to prepare the > expected output. > > Otherwise this round should be ready, modulo possible typoes. I have two smallish comments, but neither of them really have to be addressed. Overall I very much agree with this iteration and think that it's the right way to go. Thanks! Patrick
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