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Different rebase backends have different treatment for commits which start empty (i.e. have no changes relative to their parent), and the --keep-empty option was added at some point to allow adjusting behavior. The handling of commits which start empty is actually quite similar to commitb00bf1c9a8(git-rebase: make --allow-empty-message the default, 2018-06-27), which pointed out that the behavior for various backends is often more happenstance than design. The specific change made in that commit is actually quite relevant as well and much of the logic there directly applies here. It makes a lot of sense in 'git commit' to error out on the creation of empty commits, unless an override flag is provided. However, once someone determines that there is a rare case that merits using the manual override to create such a commit, it is somewhere between annoying and harmful to have to take extra steps to keep such intentional commits around. Granted, empty commits are quite rare, which is why handling of them doesn't get considered much and folks tend to defer to existing (accidental) behavior and assume there was a reason for it, leading them to just add flags (--keep-empty in this case) that allow them to override the bad defaults. Fix the interactive backend so that --keep-empty is the default, much like we did with --allow-empty-message. The am backend should also be fixed to have --keep-empty semantics for commits that start empty, but that is not included in this patch other than a testcase documenting the failure. Note that there was one test in t3421 which appears to have been written expecting --keep-empty to not be the default as correct behavior. This test was introduced in commit00b8be5a4d("add tests for rebasing of empty commits", 2013-06-06), which was part of a series focusing on rebase topology and which had an interesting original cover letter at https://lore.kernel.org/git/1347949878-12578-1-git-send-email-martinvonz@gmail.com/ which noted Your input especially appreciated on whether you agree with the intent of the test cases. and then went into a long example about how one of the many tests added had several questions about whether it was correct. As such, I believe most the tests in that series were about testing rebase topology with as many different flags as possible and were not trying to state in general how those flags should behave otherwise. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
111 lines
4 KiB
Bash
Executable file
111 lines
4 KiB
Bash
Executable file
#!/bin/sh
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test_description='git rebase tests for -Xsubtree
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This test runs git rebase and tests the subtree strategy.
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'
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. ./test-lib.sh
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. "$TEST_DIRECTORY"/lib-rebase.sh
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commit_message() {
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git log --pretty=format:%s -1 "$1"
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}
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# There are a few bugs in the rebase with regards to the subtree strategy, and
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# this test script tries to document them. First, the following commit history
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# is generated (the onelines are shown, time flows from left to right):
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#
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# master1 - master2 - master3
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# \
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# README ---------------------- Add subproject master - master4 - files_subtree/master5
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#
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# Where the merge moves the files master[123].t into the subdirectory
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# files_subtree/ and master4 as well as files_subtree/master5 add files to that
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# directory directly.
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#
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# Then, in subsequent test cases, `git filter-branch` is used to distill just
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# the commits that touch files_subtree/. To give it a final pre-rebase touch,
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# an empty commit is added on top. The pre-rebase commit history looks like
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# this:
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#
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# Add subproject master - master4 - files_subtree/master5 - Empty commit
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#
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# where the root commit adds three files: master1.t, master2.t and master3.t.
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#
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# This commit history is then rebased onto `master3` with the
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# `-Xsubtree=files_subtree` option in three different ways:
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#
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# 1. using `--preserve-merges`
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# 2. using `--preserve-merges` and --keep-empty
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# 3. without specifying a rebase backend
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test_expect_success 'setup' '
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test_commit README &&
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git init files &&
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test_commit -C files master1 &&
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test_commit -C files master2 &&
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test_commit -C files master3 &&
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: perform subtree merge into files_subtree/ &&
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git fetch files refs/heads/master:refs/heads/files-master &&
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git merge -s ours --no-commit --allow-unrelated-histories \
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files-master &&
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git read-tree --prefix=files_subtree -u files-master &&
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git commit -m "Add subproject master" &&
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: add two extra commits to rebase &&
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test_commit -C files_subtree master4 &&
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test_commit files_subtree/master5 &&
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git checkout -b to-rebase &&
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git fast-export --no-data HEAD -- files_subtree/ |
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sed -e "s%\([0-9a-f]\{40\} \)files_subtree/%\1%" |
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git fast-import --force --quiet &&
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git reset --hard &&
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git commit -m "Empty commit" --allow-empty
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'
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# FAILURE: Does not preserve master4.
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test_expect_failure REBASE_P 'Rebase -Xsubtree --preserve-merges --onto commit' '
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reset_rebase &&
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git checkout -b rebase-preserve-merges to-rebase &&
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git rebase -Xsubtree=files_subtree --preserve-merges --onto files-master master &&
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verbose test "$(commit_message HEAD~)" = "master4" &&
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verbose test "$(commit_message HEAD)" = "files_subtree/master5"
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'
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# FAILURE: Does not preserve master4.
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test_expect_failure REBASE_P 'Rebase -Xsubtree --keep-empty --preserve-merges --onto commit' '
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reset_rebase &&
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git checkout -b rebase-keep-empty to-rebase &&
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git rebase -Xsubtree=files_subtree --keep-empty --preserve-merges --onto files-master master &&
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verbose test "$(commit_message HEAD~2)" = "master4" &&
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verbose test "$(commit_message HEAD~)" = "files_subtree/master5" &&
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verbose test "$(commit_message HEAD)" = "Empty commit"
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'
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test_expect_success 'Rebase -Xsubtree --onto commit' '
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reset_rebase &&
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git checkout -b rebase-onto to-rebase &&
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test_must_fail git rebase -Xsubtree=files_subtree --onto files-master master &&
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: first pick results in no changes &&
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git rebase --skip &&
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verbose test "$(commit_message HEAD~2)" = "master4" &&
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verbose test "$(commit_message HEAD~)" = "files_subtree/master5" &&
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verbose test "$(commit_message HEAD)" = "Empty commit"
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'
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test_expect_success 'Rebase -Xsubtree --rebase-merges --onto commit' '
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reset_rebase &&
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git checkout -b rebase-merges-onto to-rebase &&
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test_must_fail git rebase -Xsubtree=files_subtree --rebase-merges --onto files-master --root &&
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: first pick results in no changes &&
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git rebase --skip &&
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verbose test "$(commit_message HEAD~2)" = "master4" &&
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verbose test "$(commit_message HEAD~)" = "files_subtree/master5" &&
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verbose test "$(commit_message HEAD)" = "Empty commit"
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'
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test_done
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