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The test for "no shallow lines after receiving ACK ready" is very sensitive to the timestamps of the commits we create. It's looking for the fetch negotiation to send a "ready", which in turn depends on the order in which we traverse commits during the negotiation. It works reliably now because the base commit "7" is created without test_commit, and thus gets a commit time matching the current system clock. Whereas the new commits created in this test do use test_commit, and get the usual test_tick time from 2005. So the fetch into the "clone" repository results in a commit graph like this (I omitted some of the "unrelated" commits for clarity; they're all just a sequence of test_ticks): $ git log --graph --format='%ct %s %d' * 1112912953 new (origin/master, origin/HEAD) * 1594322236 7 (grafted, master) * 1112912893 unrelated15 (origin/unrelated15, unrelated15) [...] * 1112912053 unrelated1 (origin/unrelated1, unrelated1) * 1112911993 new-too (HEAD -> newnew, tag: new-too) The important things to see are: - "7" is way in the future compared to the other commits - "new-too" in the fetching repo is older than "new" (and its "unrelated" ancestors) in the shallow repo If we change our "setup shallow clone" step to use test_tick, too (and get rid of the dependency on the system clock), then the test will fail. The resulting graph looks like this: $ git log --graph --format='%ct %s %d' * 1112913373 new (origin/master, origin/HEAD) * 1112912353 7 (grafted, master) * 1112913313 unrelated15 (origin/unrelated15, unrelated15) [...] * 1112912473 unrelated1 (origin/unrelated1, unrelated1) * 1112912413 new-too (HEAD -> newnew, tag: new-too) Our "new-too" is still older than "new" and "unrelated", but now "7" is older than all of them (because it advanced test_tick, which the other tests built on top of). In the original, we advertised "7" as the first "have" before anything else, but now "new-too" is more recent. You'd see the same thing in the unlikely event that the system clock was set before our test_tick default in 2005. Let's make the timing requirements more explicit. The important thing is that the client advertise all of its shared commits first, before presenting its unique "new-too" commit. We can do that and get rid of the system clock dependency at the same time by creating all of the shared commits around time X (using test_tick), and then creating "new-too" with some time long before X. The resulting graph looks like this: $ git log --graph --format='%ct %s %d' * 1500001380 new (origin/master, origin/HEAD) * 1500000420 7 (grafted, master) * 1500001320 unrelated15 (origin/unrelated15, unrelated15) [...] * 1500000480 unrelated1 (origin/unrelated1, unrelated1) * 1400000060 new-too (HEAD -> newnew, tag: new-too) That also lets us get rid of the hacky test_tick added by f0e802ca (t5539: update a flaky test, 2014-07-14). That was clearly dancing around the same problem, but only addressed the relationship between commits created in the two subshells (which did use test_tick, but overlapped because increments of test_tick in subshells are lost). Now that we're using consistent and well-placed times for both lines of history, we don't have to care about a one-tick difference between the two sides. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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