On 8/14/2020 3:25 PM, Junio C Hamano wrote: > "Derrick Stolee via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes: > >> As discussed [1], there is some concern around binary file formats requiring >> the context of the repository config in order to infer hash lengths. Two >> formats that were designed with the hash transition in mind (commit-graph >> and multi-pack-index) have bytes available to indicate the hash algorithm >> used. Let's actually update these formats to be more self-contained with the >> two hash algorithms being available. >> ... >> If this is the way we want to go with the formats, then I'll assist >> coordinating these textual and semantic merge conflicts. > > I agree that the files should be self-identifying, but have these > changes tested without sha256 hash? All of the test scripts pass with and without GIT_TEST_DEFAULT_HASH=sha256, and this test in t5318 (and a similar one in t5319) are explicit about testing both options: +test_expect_success 'warn on improper hash version' ' + git init --object-format=sha1 sha1 && + ( + cd sha1 && + test_commit 1 && + git commit-graph write --reachable && + mv .git/objects/info/commit-graph ../cg-sha1 + ) && + git init --object-format=sha256 sha256 && + ( + cd sha256 && + test_commit 1 && + git commit-graph write --reachable && + mv .git/objects/info/commit-graph ../cg-sha256 + ) && + ( + cd sha1 && + mv ../cg-sha256 .git/objects/info/commit-graph && + git log -1 2>err && + test_i18ngrep "commit-graph hash version 2 does not match version 1" err + ) && + ( + cd sha256 && + mv ../cg-sha1 .git/objects/info/commit-graph && + git log -1 2>err && + test_i18ngrep "commit-graph hash version 1 does not match version 2" err + ) +' + Since this tests exactly that the "hash version" byte is the same in a SHA-1 repo, this checks that the new version of Git writes backwards- compatible data in SHA-1 repos. Or are you hinting at a more subtle test scenario that I missed? Thanks, -Stolee
